2025 | |
Tuesday January 7 10:00 | Postdoc seminar / séminaire postdoc Emma AYÇOBERRY (LCS)
Thermal Sunyaev-Zel’dovich power spectrum: analytical model and measurement in simulations
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday January 14 10:00 | Postdoc seminar / séminaire postdoc Maximilien FRANCO (LCEG)
Characterization of the brightest galaxies during the Epoch of Reionization in COSMOS-Web
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday January 21 10:00 | Recent hiree seminar / séminaire arrivant récent Ugo LEBREUILLY (LMPA)
Gas and dust evolution during protoplanetary disk formation
Local contact: Ugo LEBREUILLY; organization: Frédéric GALLIANO |
Tuesday January 28 10:00 | Samuel LANDER (University of East Anglia)
The first five minutes in the life of a neutron star's magnetic field
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 4 10:00 | Postdoc seminar / séminaire postdoc Arthur LE SAUX (LDE3)
Unveiling stellar internal dynamics with hydrodynamical simulations
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 11 10:00 | Postdoc seminar / séminaire postdoc Roberta GIUFFRIDA (LEPCHE)
[TBA]
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 18 | Vacations / Vacances Vacances d'hiver |
Tuesday February 25 | Vacations / Vacances Vacances d'hiver |
Tuesday March 4 10:00 | Postdoc seminar / séminaire postdoc Joey MOMBARG (LDE3)
The next step in stellar evolution: towards multi-dimensional models
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday March 11 10:00 | Postdoc seminar / séminaire postdoc Cail DALEY (LCS)
CMB Lensing Measurements with Two Years of Data from the SPT-3G Survey
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday March 18 10:00 | [TBA] |
Tuesday March 25 10:00 | [TBA] |
Tuesday April 1 10:00 | Evan O'CONNOR (Stockholm University, Sweden)
Recent Advances in Core-Collapse Theory
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday April 8 10:00 | LCS invitee (Array)
.
Local contact: [-]; organization: [-] |
Tuesday April 15 | Vacations / Vacances Vacances de printemps |
Tuesday April 22 | Vacations / Vacances Vacances de printemps |
Tuesday April 29 10:00 | [TBA] |
Tuesday May 6 10:00 | [TBA] |
Tuesday May 13 10:00 | [TBA] |
Tuesday May 20 10:00 | Natascha FORSTER SCHREIBER (Max-Planck-Institut für extraterrestrische Physik)
Star-Forming Galaxies at Cosmic Noon and Beyond
Local contact: Emanuele DADDI; organization: Frédéric GALLIANO |
Tuesday May 27 10:00 | [TBA] |
Tuesday June 3 10:00 | [TBA] |
Tuesday June 10 10:00 | [TBA] |
Tuesday June 17 10:00 | [TBA] |
Tuesday June 24 10:00 | [TBA] |
SUMMER BREAK |
2024 | |
Tuesday January 9 10:00 | Roya MOHAYAEE (IAP)
The Anomalous Dipole
[click here for abstract] Standard model of cosmology is based on the cosmological principle, which states that the Universe is statistically homogeneous and isotropic on large scales. Is this hypothesis supported by the observations ? After a historical survey of the field, I shall use the high redshift data from
radio galaxies and quasars to show that the early Universe does not seem to be isotropic and the rest frame of cosmic microwave background radiation does not coincide with the rest frame of distant sources. I shall also demonstrate that the cosmological principle is violated at a statistical significance of over 5-sigma. Local contact: Réza ANSARI; organization: Frédéric GALLIANO |
Tuesday January 16 10:00 | Cancelled / séminaire annulé Jose Ignacio "Nacho" ANEZ LOPEZ (LFEMI)
Signatures of magnetic braking in Class 0 protostars ? Exploring the gas kinematics in magnetized models of low-mass star formation
[click here for abstract] The role of magnetic braking in regulating gravitational collapse and circumstellar disk during the main accretion phase, is an open question. While only indirect evidence was found from observational work, such as compact disk sizes and the launching of high-velocity collimated jets, we aim at more direct tests of the magnetic braking in observations. The study of polarized dust emission as a tracer of the magnetic field and molecular line emission as a tracer of gas kinematics in young protostars can provide valuable information for understanding how the presence of the magnetic field affects the accretion process.
In the present work, we have used both non-ideal MHD models and synthetic observations from the radiative transfer of protostellar formation to put constraints on the magnetically-regulated disk formation scenario. We use our model synthetic observations to identify possible direct signatures of the magnetic braking from the maps of the molecular gas emission. By comparing the specific angular momentum of two similar models that differ in magnetic flux, we see that the more magnetized model shows a higher angular momentum redistribution above 1000 au. In addition, we have tested the methods typically used to infer the specific angular momentum from an observational point of view. We have found possible observational evidence of magnetic braking in the kinematics of the C18O(2-1) molecule, such as a flattening of the radial profile of specific angular momentum for radii smaller than 1000 au for the more magnetized model similar to the characteristics found in observational work. On the other hand, in this study we show that the maximum velocity computed in the equatorial plane, which is traditionally used as an approximation of the rotational velocity, may overestimate the rotational velocity, probably due to contamination from radial motions. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday January 23 10:00 | Francisca KEMPER (Institute of Space Sciences (ICE-CSIC) / ICREA / IEEC, Spain)
The interstellar dust reservoir in galaxies
[click here for abstract] The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. However, far-infrared and submillimeter studies have revealed enormous dust masses at high redshifts that are difficult to explain with dust production from evolved stars (the so-called "dust budget problem"), while in the nearby universe there is also a significant mismatch between the dust production rate and the dust mass observed in the interstellar medium of galaxies. I will go over some possible explanations in an attempt to find a way forward towards a solution to this seeming discrepancy. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday January 30 10:00 | Florian PACAUD (University of Bonn)
Galaxy clusters and filaments in the first eROSITA all-Sky survey
[click here for abstract] Launched in July 2019, eROSITA was set to survey the sky in the soft X-ray band for four years and provide a much awaited update to the old ROSAT all-sky survey. In a few weeks, the collaboration will release the first all-sky map obtained from the first six month of observation. In this talk, I will present the instrument and its technical abilities. I will then explore the all-sky map and show selected results on individual local clusters and filaments. Finally, I will give a preview of the soon-to-be-released data products, including AGN and galaxy catalogs, and present some of the methods used for their cosmological analysis. Local contact: Marguerite PIERRE; organization: Frédéric GALLIANO |
Tuesday February 6 10:00 | Stefanie WALCH-GASSNER (University of Köln)
The impact of stellar feedback on different scales and galactic environments
[click here for abstract] Stellar feedback refers to the processes by which massive stars release energy, radiation and material into their surroundings, influencing the structure and evolution of the galaxies in which they reside. Understanding the impact of stellar feedback on different galactic environments is crucial for developing a comprehensive picture of galaxy formation and evolution. In this context, different galactic environments refer to regions within a galaxy that differ in their physical conditions, such as the average gas density, temperature, or metallicity.
We study the respective impact of stellar winds, ionizing radiation, and supernovae in modern simulations of the multi-phase interstellar medium in parts of galaxies within the SILCC project, which I will present in this talk. From these galactic scale simulations we find that ionizing radiation is the most important factor in regulating the star formation rate, while supernova over-pressure the gas substantially, thus driving a galactic outflow. Local contact: Suzanne MADDEN; organization: Frédéric GALLIANO |
Tuesday February 13 10:00 | Jonathan TAN (Chalmers & University of Virginia)
A Light in the Dark - Massive Star Birth Through Cosmic Time
[click here for abstract] Massive stars are important thoughout the universe, but their formation remains poorly understood. I review current understanding of how massive stars and star clusters form in our Galaxy, including models for how star formation is triggered in giant molecular clouds and tests of how individual massive stars form from smaller scale clumps and cores. Finally, I discuss how massive star formation may have been different in the very early universe and how the first stars may have seeded the supermassive black holes powering active galactic nuclei. Local contact: Philippe ANDRÉ; organization: Frédéric GALLIANO |
Tuesday February 20 | Vacations / Vacances Vacances d'hiver |
Tuesday February 27 10:00 | Hakim ATEK (IAP)
Unveiling the faintest and the brightest galaxies at early times with JWST
[click here for abstract] The JWST is revolutionizing our understanding of the early Universe by unveiling a wealth of bright galaxies at z>9 and faint AGNs at z>5. I will present the latest constraints on the overabundance of UV-bright galaxies at z>9, which is 10-100 times higher than galaxy formation models. I will discuss to what extent recent theoretical efforts can reproduce such observations, and how future wide-area surveys such as Euclid will help put stronger constraints ion the bright-end of UVLF at z>8. On the other hand, faint galaxies, representing the building blocks of present-day galaxies, have eluded spectroscopic constraints, even with the deepest JWST campaigns so far. I will present the results of our UNCOVER survey, which combines ultra-deep NIRSpec spectroscopy with the strong lensing magnification of A2744 cluster. We characterize ultra-faint galaxies with intrinsic absolute magnitude between Muv=-17 and Muv=-15 at 6<z<8, and stellar masses down to 10^6 solar masses. I will discuss our plans to obtain the deepest observations on sky with the GLIMPSE program to the faintest galaxy population out to z=15 and beyond. Local contact: Carlos GÓMEZ GUJARRO; organization: Carlos GÓMEZ GUJARRO |
Tuesday March 5 10:00 | Recent hiree seminar / séminaire arrivant récent Emmanuel BERTIN (LCEG)
Wide-field imaging meets deep learning: new challenges, new opportunities
[click here for abstract] Since the 19th century, wide-field imaging has significantly advanced numerous fields of Astrophysics, spanning from the study of solar system bodies to observational cosmology. Ongoing and future optical/near-infrared imaging surveys face many interesting data analysis challenges, especially in time domain astronomy, in a context where detector technology enable wide-field observations at increasingly high frame rates. Through concrete examples, I will show with how Deep Learning techniques offer promising solutions to address such challenges, and provide new scientific opportunities. Local contact: Emmanuel BERTIN; organization: Carlos GÓMEZ GUIJARRO |
Tuesday March 12 10:00 | Postdoc seminar / séminaire postdoc Arturo NUNEZ (LMPA)
The impact of baryonic physics in galaxy formation: Multi-scale approach to galaxy simulations, from the initial mass function to galaxies in a cosmological environment
[click here for abstract] The interplay of baryonic physics (star formation and feedback processes) in shaping galaxies and their host halos is a multiscale and multidisciplinary problem. Numerical simulations are key to understanding these processes as they cover phenomena that take place at a wide range of scales, some too small for most astrophysical observations but yet able to impact the shape and evolution of galaxies as a whole. However, no single simulation can address every aspect of this complex issue. A comprehensive approach is essential to integrate learnings from various types of simulations and compare them with observations. This includes understanding star formation histories in cosmological simulations, examining interstellar medium dynamics in comparison to simulations of individual galaxies, and exploring the non-universality in the stellar initial mass function in specific molecular cloud simulations. My goal is to discuss how simulations across different scales, together with detailed multiscale observations, collectively contribute to approaching the complexities of galaxy formation and evolution. All this while discussing current shortcomings and successes of high-resolution numerical simulations of galaxies and galactic environments.
WARNING: incomplete video recording. Local contact: Thierry FOGLIZZO; organization: Adnan Ali AHMAD |
Thursday March 14 14:00 | Remi SOUMMER & Laurent PUEVO (STScI, Baltimore)
La mission HWO (Habitable World Observatory)
[click here for abstract] Ce séminaire proposera une présentation de la mission HWO
(Habitable World Observatory).
Cette mission est la nouvelle mission phare de la NASA à laquelle nous souhaitons participer, (notamment à l’instrument grand champ, qui aura aussi pour but de l’astrométrie très précise). Les orateurs seront au DAp toute l’après-midi et pourront discuter avec les personnes intéressées. Local contact: Vianney LEBOUTEILLER; organization: Pierre-Antoine FRUGIER |
Tuesday March 19 10:00 | Postdoc seminar / séminaire postdoc Miguel FERNANDES MOITA (LISIS)
The Large Italian X-ray facility (LARIX) and the advancements in Laue lens development
[click here for abstract] The LARIX (LARge Italian X-ray facility) is a multi-project facility situated in the Scientific-Technological Pole of the University of Ferrara, housed in an underground building featuring a 100-meter-long tunnel with two large experimental rooms on each side. Dedicated to the development and testing of X- and Gamma-ray astronomy instrumentation, LARIX hosts two beamlines: the 12-meter-long LARIX-A in experimental room A, suitable for linearity tests of hard X-ray detectors, reflectivity measurements of X-ray reflector samples, and ground calibrations; and the 50-meter-long LARIX-T installed in the tunnel, ideal for testing gamma-ray reflectors and low-weight gamma-ray detector prototypes when requiring low-divergence beams or lengthy beamlines. This presentation will provide an overview of both installations, their instrumentation, past projects, and opportunities for access through collaborations or transnational access programs like AHEAD. Furthermore, we will discuss recent advancements in Laue lens development that we did in LARIX, particularly the TRILL project, supported by ASI, aimed at advancing the technological readiness of Laue lenses. Future goals include the ASTENA mission concept, submitted to the ESA program 'Voyage 2050', featuring a narrow field telescope (NFT) based on a focusing Laue lens with an energy passband from 50 to 700 keV and a 20-meter focal length, promising breakthroughs in sensitivity and angular resolution in this energy band. Additionally, we will explore innovative concepts such as a high-energy Laue lens spectro-polarimeter, inspired by the recent success of the IXPE mission. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday March 26 10:00 | Werner BECKER (MPE)
The eROSITA Mission: Status and Scientific Prospects
[click here for abstract] eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian Spektrum-Roentgen-Gamma (SRG) mission, which was successfully launched from Baikonur on July 13th, 2019. Till today, eROSITA has performed four and a half all-sky surveys, mapping the whole X-ray sky with an XMM-Newton-type sensitivity. In the 0.2-2.4 keV band, it is about 30 times more sensitive than ROSAT, while in the 2.0-8.0 keV band, it provides the first ever true imaging survey of the sky. Its design-driving science is the detection of large samples of galaxy clusters to redshifts z > 1 to study the large-scale structure in the Universe and to test cosmological models, including Dark Energy. Although considered to be „secondary science“, the currently available data provide a world of exciting new results also for galactic sources, including Neutron Stars and Pulsars, X-ray binaries, active stars, and diffuse galactic emission from, e.g., star clusters and supernova remnants. In my talk, I will report on the status of the eROSITA mission and its scientific prospects, with the main focus on selected supernova remnants and compact objects. Local contact: Jean BALLET; organization: Leïla GODINAUD |
Tuesday April 2 10:00 | James DUNLOP (University of Edinburgh)
Charting the emergence of the first galaxies with JWST
[click here for abstract] The James Webb Space Telescope (JWST) is transforming our view of galaxy formation and evolution in the young Universe. I will provide an overview of the latest results from the PRIMER survey, the largest JWST Cycle-1 “Galaxies” programme which, in combination with other public JWST imaging, is now enabling us to chart the early growth of the galaxy population back to within ~300 million years of the Big Bang. Specifically, I will present and discuss the first robust determination of the evolving galaxy luminosity function extending out to redshifts z~13, as well as new measurements of the galaxy stellar mass function reaching out to z~9. I will then attempt to interpret these results in the context of our current understanding of the evolving dark matter halo mass function and the efficiency with which galaxies are able to convert their baryons into stars. Finally, I will discuss the prospects for future progress with JWST and with the Atacama Large Millimeter Array (ALMA), including the possibility of uncovering the emergence of the first galaxies. Local contact: Carlos GÓMEZ-GUIJARRO; organization: Carlos GÓMEZ-GUIJARRO |
Tuesday April 9 | Vacations / Vacances Vacances de printemps |
Tuesday April 16 | Vacations / Vacances Vacances de printemps |
Tuesday April 23 10:00 | Florent MERTENS (Observatoire de Paris)
Unveiling the Physics of the Cosmic Dawn and the Epoch of Reionisation in the SKA era
[click here for abstract] Direct observation of the Cosmic Dawn and Epoch of Reionization via the redshifted 21-cm line will have unprecedented implications on the study of structure formation in the early Universe. This exciting goal is challenged by the difficulty of extracting the feeble 21-cm signal buried under bright astrophysical foregrounds and contaminated by numerous systematics. Several experiments such as LOFAR, MWA, HERA, and NenuFAR are underway aiming at statistically detecting the 21-cm signal fluctuations from the EoR and CD, and paving the way for the SKA EoR CD experiment which will be capable of directly image the large-scale neutral hydrogen structures from these distance epochs. In this talk, I will present recent results from the LOFAR-EoR and NenuFAR Cosmic Dawn collaborations. After publishing the deepest upper limit on the signal power-spectra at z~9, which has made it possible to set constraints on the physics of the IGM during the EoR, the LOFAR-EoR team is progressing towards a deeper upper limit on a broader range of redshift. On the Cosmic Dawn front, the NenuFAR CD team recenty published a first upper limit on the signal power-spectra at z~20. These new results will be discussed, as well as the improvements in instrument calibration and foreground mitigation that enabled these achievements. Local contact: Jérôme BOBIN; organization: Fabian HERVAS PETERS |
Friday April 26 11:00 Salle Berthelot (141) | Joint DAp-DPhP seminar / séminaire DAp-DPhP joint Christophe YÈCHE & Éric ARMENGAUD (DPhP)
DESI Year 1 Results - Cosmological Constraints from the Measurements of Baryon Acoustic Oscillations
[click here for abstract] We will present cosmological results from the measurement of baryon acoustic oscillations (BAO) in galaxy, quasar and Ly-α forest tracers from the first year of observations from the Dark Energy Spectroscopic Instrument (DESI). BAO provide robust measurements of the transverse comoving distance and Hubble rate, or their combination, relative to the sound horizon, in seven redshift bins from over 6 million extragalactic objects in the redshift range 0.1<z<4.2.
With the first six redshift bins using over 5.7 million unique galaxy and quasar redshifts measured by DESI, the combined precision of the BAO is 0.52%. The seventh BAO measurement, at redshift z~2.3 is obtained over 0.4 million Ly-α forest spectra with their auto-correlation and their cross-correlation with the spatial distribution of 0.7 million quasars. The precision for this measurement is 1.1%. Then we will present the cosmological interpretation of these BAO measurements, in the framework of the standard flat ΛCDM cosmological model. In particular we will show cosmological constraints on the Hubble parameter H0 and on the sum of neutrino mass. Finally, we will extend the interpretation to models with a constant dark energy equation of state and even to those with a time-varying dark energy equation of state. Local contact: Vanina RUHLMANN-KLEIDER & François BRUN; organization: Vanina RUHLMANN-KLEIDER & François BRUN |
Tuesday April 30 10:00 | Postdoc seminar / séminaire postdoc Dinil PALAKKATHARAPPIL (LDE3)
Precise Stellar Age Determination of Stars with Gaia and TESS: Prospects and Insights for the upcoming PLATO and HAYDN Missions
[click here for abstract] Determining precise star ages is essential for insights into stellar, exoplanetary, and galactic evolution, but it remains a complex challenge. The two most precise techniques are (1) asteroseismology, which is the study of the internal structure of stars by means of intrinsic global oscillations, and (2) analysis of stellar clusters where stars are formed from the same molecular cloud at the same time, and the observed colour-magnitude
diagram is a strong diagnostic of the cluster age. In this talk, I will combine these two techniques to determine the age of intermediate age open cluster NGC 2477. We used astrometry and colour from Gaia to extract membership probabilities and colour information about the stars in clusters, while pulsating stars were found using TESS data. Observations are complemented with asteroseismic modelling using MESA and GYRE to obtain the precise age of the cluster. In the second part of the talk, I will detail my contribution to the development of the ground segment of the ESA M3 PLATO mission to obtain stellar mass, radius, and age as well as several rotation and magnetic activity indicators for which CEA is responsible. I will conclude by showcasing some applications of the PLATO pipeline using Kepler and TESS data. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday May 7 10:00 | Thomas HENNING (Max Planck Institute for Astronomy, Heidelberg)
Towards New Horizons: Star and Planet Formation with JWST
[click here for abstract] The James Webb Space Telescope (JWST) is the most powerful space-based infrared observatory ever built. The first part of the talk will discuss the main structures of the telescope and its assembly after launch. The talk will then highlight the extremely exciting science results in the field of star and planet formation, including the nature of protostars and planet-forming disks. A special emphasis will be placed on the accretion process and the chemical building blocks of disks and what we can learn from infrared spectroscopy regarding the inventory of material in the terrestrial planet-forming zone. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday May 14 10:00 | Recent hiree seminar / séminaire arrivant récent Damien TURPIN (DAp)
The high-energy and multi-messenger transient sky in the eyes of the SVOM mission
[click here for abstract] Over the past decades, the study of highly energetic transient phenomena has led to several scientific breakthroughs from the discovery of r-process nucleosynthesis production sites to the first credible identification of ultra-high-energy cosmic-ray accelerators. In a general manner, these explosive events allow us to study extreme physical regimes (extreme gravity, extreme magnetic fields, relativistic shocks) and are unique probes to study the Universe properties up to high redshift. In the last 10 years, an unprecedented amount of new generation instruments observing the sky at all wavelengths and with all astrophysical messengers have significantly contributed to enlarging our vision of the transient sky phenomena. This observational revolution initiated by the gravitational wave interferometers has forced the astrophysical community to rapidly adapt to the new challenges of multi-messenger astronomy. In June 2024, the French community will have a leading role in this young research domain with a strong implication for the French lab. in the upcoming SVOM mission. In this seminar, I will review some of the latest results obtained by the scientific community exploring the high-energy transient sky, especially with a focus on the sources of interest for the SVOM mission. I will show how important will be the SVOM mission contribution to this exciting field of research that has probably revealed only a subset of its richness. Local contact: Damien TURPIN; organization: Frédéric GALLIANO |
Tuesday May 21 10:00 | Climate seminar / séminaire climat Céline GUIVARCH (École des Ponts ParisTech)
Le changement climatique vu à travers les lunettes d’une économiste
[click here for abstract] Les effets du changement climatique constituent une menace grandissante pour nos sociétés et nos économies; et agir face à cette menace nécessite de transformer nos façons de nous déplacer, nous loger, de produire et consommer. Autant de questions pour l'économie, pour analyser les implications économiques des trajectoires et politiques publiques d'atténuation du changement climatique. Ce séminaire proposera quelques incursions dans la recherche actuelle en économie du changement climatique, à partir d'un échantillon d'articles récents.
Le séminaire sera en français avec des slides en anglais. Local contact: Roland LEHOUCQ & Jérôme GUILET; organization: Roland LEHOUCQ & Jérôme GUILET |
Tuesday May 28 10:00 | Paul GOLDSMITH (JPL)
Velocity-Resolved Fine Structure Line Observations and Star Formation: New Results and New Capabilities
[click here for abstract] What controls star formation? is a key question in astrophysics, and one very important aspect of this is the interaction of newly-formed stars with their surroundings. The radiative and mechanical feedback from young, massive stars can be dramatic. The altered composition and
increased temperature that result make atomic and ionic fine structure lines ideal probes of stellar feedback. The value of such observations is dramatically increased if the spectral lines are velocity-resolved so that the momentum and energy impact on the stars’ surroundings can be determined. But such observations must be carried out from suborbital or space observatories due to absorption in the Earth’s atmosphere. The fine structure lines of ionized
carbon, and atomic oxygen are the most important and have been widely observed with high spectral resolution starting with the Herschel HIFI instrument and continuing with upGREAT on SOFIA. In this talk I will discuss some recent fine structure line observations focusing on the effects of star formation on the surrounding interstellar medium and possible problems with measuring the rate of star formation. I will conclude by presenting two fine structure line spectroscopic balloon missions. GUSTO was launched on 31 December 2023, and until 27 February 2024 surveyed the 205 μm line of [NII] and 158 μm line of [CII] in the central portion of the Milky Way and the Large Magellanic Cloud. ASTHROS, which is to follow at the end of 2024, has a much larger 2.5m diameter telescope, and will observe both [NII] fine structure lines to derive the electron density in selected regions. Local contact: Suzanne MADDEN; organization: Frédéric GALLIANO |
Tuesday June 4 | Special event / Événement spécial Semaine de la SF2A |
Tuesday June 11 10:00 | Mustapha MEFTAH (LATMOS)
Les NanoSatellites au service de l’observation de la Terre et de l’univers
[click here for abstract] Le thème de la conférence portera sur l’observation de la Terre, le climat, les satellites et le NewSpace. Le 24 janvier 2021, une fusée Falcon 9 était lancée avec succès par SpaceX depuis Cap Canaveral, en Floride. Sous la coiffe du lanceur, il y avait 143 satellites. C’est à ce jour le plus grand nombre de satellites jamais déployés en une seule mission. Uvsq-Sat, premier nanosatellite français dédié à l’observation de variables climatiques essentielles, faisait partie de cette épopée. Depuis plus de trois ans, Uvsq-Sat observe la Terre et le Soleil de manière assidue. A 550 km d’altitude, ce satellite mesure la quantité d'énergie solaire réfléchie vers l'espace et la quantité d'énergie thermique émise par la Terre vers l’espace.
Local contact: Henri TRIOU; organization: Pierre-Antoine FRUGIER |
Tuesday June 18 10:00 | Cancelled / séminaire annulé Maxime LOMBART (LFEMI)
How to treat dust coagulation/fragmentation in 3D hydrodynamic simulations ?
[click here for abstract] Particles coagulation and fragmentation are ubiquitous (raindrop formation, air pollution, combustion, polymerization, astrophysics) and mathematically described by the Smoluchowski coagulation and the fragmentation equations. Several processes such as gas/particles dynamics, chemical reaction and radiative transfer depends on the evolution of the particle size distribution governed by coagulation/fragmentation. Tracking the size evolution of particles in 3D simulation is key for understanding, for instance, cloud formation and planet formation. Therefore, these equations must be accurately solved while preserving computational costs, which is a tremendous numerical challenge. However, current algorithms for solving coagulation/fragmentation suffer from an over-diffusion in the conditions of 3D simulations. To tackle this challenge, we developed a discontinuous Galerkin scheme to efficiently solve the conservative form of the coagulation/fragmentation equation. In particular, we aim to perform the first 3D simulations of dusty protoplanetary discs and protostellar collapse that include realistic coagulation/fragmentation. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday June 25 10:00 | Jérôme RODRIGUEZ, Bertrand CORDIER & Damien TURPIN (DAp)
The SVOM Launch: En route for the transient hunt
[click here for abstract] The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a Sino-French mission planned to be launched on June 22nd 2024 from Xichang China. The launch of the satellite opens the time when scientists will step up and start exploiting the data. SVOM, however, is already a long-term project during which the involvement of engineers, developers, and scientists has already been huge. In this presentation I will overview some of the aspects of the mission, the scientific programs and aims of the project, but also recall its history and try and acknowledge the involvement of many colleagues which permitted the achievement of this fantastic machine. I will also introduce some of the novelties and specificities of the mission, in particular all the aspects dedicated to the time domain astronomy and real time analysis, implying the development of a dedicated science center, specific tools, and shifts for a certain of us as burst advocates. Finally we will (try to) have a zoom with those of us that have attended the launch in China, so that they can share with us their feeling of the launch and first impressions post launch, in this opening scientific exploitation era.
The talk will be given in French with slides in English. Local contact: Pierre-Antoine FRUGIER; organization: Frédéric GALLIANO |
SUMMER BREAK | |
Tuesday September 10 10:00 | Postdoc seminar / séminaire postdoc Maxime LOMBART (LFEMI)
How to treat dust coagulation/fragmentation in 3D hydrodynamic simulations ?
[click here for abstract] Particles coagulation and fragmentation are ubiquitous (raindrop formation, air pollution, combustion, polymerization, astrophysics) and mathematically described by the Smoluchowski coagulation and the fragmentation equations. Several processes such as gas/particles dynamics, chemical reaction and radiative transfer depends on the evolution of the particle size distribution governed by coagulation/fragmentation. Tracking the size evolution of particles in 3D simulation is key for understanding, for instance, cloud formation and planet formation. Therefore, these equations must be accurately solved while preserving computational costs, which is a tremendous numerical challenge. However, current algorithms for solving coagulation/fragmentation suffer from an over-diffusion in the conditions of 3D simulations. To tackle this challenge, we developed a discontinuous Galerkin scheme to efficiently solve the conservative form of the coagulation/fragmentation equation. In particular, we aim to perform the first 3D simulations of dusty protoplanetary discs and protostellar collapse that include realistic coagulation/fragmentation. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday September 17 10:00 | Postdoc seminar / séminaire postdoc Arghyadeep PAUL (LDE3)
Star-Planet Magnetic Interactions: From Solar System to Exoplanets
[click here for abstract] The interaction between stellar winds and planetary magnetospheres has been a focus of research for decades. Within the heliospheric context, star-planet interactions similar to that between the Sun and the Earth reshapes the planet’s local magnetic environment leading to the formation of magnetospheres. Magnetic reconnection within these magnetospheres gives rise to helical magnetic flux ropes known as flux transfer events (FTEs). We developed a two-way coupled magnetosphere-ionosphere model to investigate the impact of FTEs on the planet’s ionosphere. For a specific case of an Earth like planet, the field aligned currents generated by these FTEs closely resemble observations of discrete dayside auroral arcs, suggesting FTEs to be a probable cause. In the context of exoplanetary systems, star-planet interactions vary depending on the planet's orbital location. For close-in orbits located in the sub-Alfvénic stellar wind, the Poynting flux generated by star-planet interactions can propagate toward the star, giving rise to stellar chromospheric hotspots. Our current work characterises and quantifies the efficiency of this energy transfer
between the planet and the star, revealing that a significant portion of the energy never reaches the star and is reflected by the stellar transition region back toward the planet. The firm detection and characterisation of such magnetic interactions from observations of chromospheric hotspots would also lead to constraints on the amplitude of the magnetic field of exoplanets, to which we are blind so far. Future research, utilising the previously developed magnetosphere-ionosphere model, will also explore how the presence or absence of a planetary ionosphere influences the Poynting flux generated by the planet. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday September 24 10:00 | Postdoc seminar / séminaire postdoc Jesse PALMERIO (LISIS)
Scientific objectives of SVOM Gamma-Ray Burst follow-up with large telescopes
[click here for abstract] Discovered over 50 years ago, Gamma-Ray Bursts are brief flashes of high-energy photons so bright they can outshine the entire rest of the Universe during their brightest moments. These second-to-minute-long flashes, called the prompt emission, are followed by an afterglow that shines across the electromagnetic spectrum, from the radio up to TeV, and that fades over the following hours/days (or up to years in the radio). The prompt emission originates from energy dissipation within an ultra-relativistic jet produced during the formation of a stellar-mass compact object (neutron star or black hole) while the afterglow is explained as synchrotron emission from the deceleration of the jet by the surrounding medium.
GRBs have been divided into two populations (historically, based on the duration of their prompt emission, although recently this criteria is being put into question): Long GRBs (LGRBs) which are produced by the collapse of a massive star and Short GRBs (SGRBs) which are produced by the merger of two compact objects. In the last 20 years, both populations have proven themselves to be exceptional probes of the Universe, in large part thanks to dedicated follow-up campaigns designed to catch the afterglow before it fades. In this talk, I will highlight some of the recent scientific results and opportunities offered by the follow-up with large telescopes (mainly the VLT). I will discuss the implications for other astrophysical fields beyond GRB science (such as cosmology, galaxy evolution, dust, chemical enrichment, star formation…), the challenges of such studies and the prospectives for SVOM GRBs. Local contact: Thierry FOGLIZZO; organization: Ugo LEBREUILLY |
Wednesday September 25 11:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Vincent TATISCHEFF (IJClab)
COMCUBE-S : un essaim de nanosatellites pour la polarimétrie des sursauts gamma et l'astronomie multi-messagers.
[click here for abstract] L'astronomie multi-messagers et multi-longueurs d'onde nécessite une surveillance en continu du ciel dans le domaine des rayons gamma pour détecter et localiser rapidement les sursauts gamma produits lors de la collision d'astres compacts ou l'implosion d'une étoile super-massive. Plusieurs missions spatiales de nanosatellites dédiés à la détection des sursauts gamma sont en cours de développement dans le monde. Le projet COMCUBE-S vise à apporter une nouvelle dimension à ce réseau de CubeSat en y ajoutant des mesures de la polarisation linéaire de l'émission prompte des sursauts gamma. Ces mesures peuvent fournir un diagnostic inédit de la physique des jets ultra-relativistes produits dans les sursauts, ainsi que de la nature de leur progéniteur astrophysique.
COMCUBE-S a récemment été sélectionné par l'ESA pour une étude de Phase A, en vue de la mise sur orbite d'une constellation de 27 nanosatellites avant la fin de la décennie. La charge utile des satellites est un télescope de type Compton optimisé pour la polarimétrie gamma, dont un premier prototype a pu être testé par des expériences sous ballon stratosphérique avec le CNES. Dans ce séminaire, nous présenterons le vol transatlantique réalisé en juin dernier et le projet CubeSat avec l'ESA. Local contact: Philippe LAURENT; organization: Philippe LAURENT |
Tuesday October 1 10:00 | Recent hiree seminar / séminaire arrivant récent Elsa DUCROT (LDE3)
Detection and characterization of rocky planets around ultra-cool stars
[click here for abstract] The launch of the James Webb Space Telescope (JWST) marked a significant milestone in the field of exoplanet research. For the first time, we can study the atmospheres of Earth-sized rocky planets—an opportunity that was previously unattainable. However, this is currently possible only around the coolest stars, known as red dwarfs. These stars are ideal targets for several reasons: (1) their smaller size makes it easier to detect and study small, transiting planets; (2) their lower luminosity leads to more frequent planetary transits for the same level of stellar irradiation; (3) they are the most abundant stars in the galaxy, and (4) planets orbiting them are more likely to be rocky planets with short orbital periods. In the near future, only such planetary systems are expected to produce signal-to-noise ratios (SNRs) high enough to confidently confirm or rule out the presence of atmospheres on potentially habitable planets.
In this context, my research focuses on: (1) detecting new rocky, temperate planets around red dwarfs using the SPECULOOS telescopes, and (2) observing these planets with JWST to assess the presence and composition of their atmospheres or determine the nature of their surfaces. In this talk, I will share insights into these areas of my work, including the discovery of the new SPECULOOS-3b exoplanetary system and the detailed characterization of TRAPPIST-1's innermost planets using JWST data. I will also discuss stellar contamination caused by photometric heterogeneities, which represents the primary challenge in characterizing planets around red dwarfs in transit, along with various strategies to overcome this obstacle. Finally, I will offer some perspectives on the future study of rocky planets orbiting red dwarfs. WARNING: the first minutes of the recording are missing. Local contact: Elsa DUCROT; organization: Antoine STRUGAREK |
Tuesday October 8 10:00 | Lorenzo DUCCI (University of Tübingen)
Accretion anomalies: a journey through fast transients phenomena and accretion instabilities in X-ray binaries
[click here for abstract] Accretion onto compact objects, such as black holes and neutron stars, is a fundamental process in astrophysics, powering some of the most luminous objects in the universe. In X-ray binaries, the accretion of matter from a companion star onto the compact object leads to the emission of intense X-ray radiation. While the general framework of accretion is well understood, there exist peculiar and enigmatic fast flaring activities exhibited by different types of X-ray binaries, which challenge our current understanding of these systems.
In this seminar, I will delve into the diverse flaring behaviors observed in various X-ray binaries, highlighting their extreme properties. I will then discuss the possible mechanisms that have been proposed to explain these events. By exploring them, we can gain insights into the underlying physics of accretion and the behavior of matter in extreme environments. Finally, I will outline the future prospects for studying these enigmatic events, including the potential for new discoveries with upcoming X-ray missions. Local contact: Diego GÖTZ; organization: Frédéric GALLIANO |
Tuesday October 15 10:00 | Climate seminar / séminaire climat Sophie SCHBATH (INRAE)
Parcours du laboratoire MaIAGE pour réduire l'empreinte environnementale de ses activités
[click here for abstract] L'unité MaIAGE a commencé à réfléchir et adopter des éco-gestes dès 2017. En 2020, elle réalise son premier bilan de gaz à effet de serre (GES) sur les données de 2019 et se porte volontaire en 2021 pour participer à l'expérimentation nationale du GDR Labo 1point5. Cette expérimentation, conduite sur 22 labos pilotes, vise à étudier la mise en mouvement des laboratoires vers une réduction de leurs émissions de GES et à explorer différents dispositifs de réduction. C'est dans ce cadre que l'unité a voté en 2022 un scénario visant 40% de réduction de ses GES en 2030 ; ce scénario s'accompagne d'un certain nombre de mesures obligatoires et/ou incitatives. C'est l'ensemble de ce parcours qui sera présenté lors de la présentation avec des exemples d'actions réalisées et de premiers résultats. Local contact: Jérôme GUILET & Roland LEHOUCQ; organization: Frédéric GALLIANO |
Wednesday October 16 10:00 | Daisuke NAGAI (Yale University, USA)
Cosmology in the Era of Multi-Wavelength Astronomical Surveys
[click here for abstract] We are entering the golden age of multi-wavelength astronomical surveys. In the 2020s, a plethora of surveys (such as Euclid, eROSITA, Rubin-LSST, Simons Observatory, and CMB-S4) are underway or planned to provide unprecedented insights into cosmology and galaxy formation. In this talk, I will provide a brief overview of significant scientific opportunities and the notable challenges in the era of big data, with highlights on recent advances in computational modeling and the integral roles played by artificial intelligence and machine learning. Local contact: Marguerite PIERRE; organization: Frédéric GALLIANO |
Tuesday October 22 | Vacations / Vacances Vacances de la Toussaint |
Tuesday October 29 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Eric Faustino JIMÉNEZ-ANDRADE (National Autonomous University of Mexico)
The next generation VLA (ngVLA) and the participation of Mexico
[click here for abstract] The ngVLA, led by the National Radio Astronomy Observatory, will be the largest radio interferometer ever built in the northern hemisphere. With 263 antennas distributed across the US, Canada, and Mexico, the array will reach spatial resolutions and sensitivities without precedents. Operating from 1.2 GHz (∼ 21 cm) to 116 GHz (2.6 mm), the ngVLA will open a new window on the universe through ultra-sensitive imaging of spectral lines and continuum emission with milliarcsecond resolution. In this talk, we will review the project, its timeline, and its main scientific drivers. We will discuss, in particular, how the ngVLA will contribute to our understanding of galaxy evolution via deep radio continuum and CO line surveys. We will also cover the role of the National Autonomous University of Mexico (UNAM) and the Mexican community in the ngVLA project. UNAM scientists are exploring potential sites for antennas in Mexico and contributing to the array and antenna foundation designs. Finally, we will describe how UNAM is leading the efforts to establish a Mexican University Consortium to support the ngVLA project. Local contact: Benjamin MAGNELLI; organization: Benjamin MAGNELLI |
Tuesday October 29 | Vacations / Vacances Vacances de la Toussaint |
Tuesday November 5 10:00 | Special seminar / séminaire exceptionnel Jean-Marc BONNET-BIDAUD (DAp)
Chine, la civilisation du ciel transitoire
[click here for abstract] En Chine, dès l'époque classique des Han (IIe siècle AEC), le Ciel est conçu comme le miroir de la Terre, lieux d'évènements fortuits (éclipses, comètes, taches solaires, novae et supernovae,..) qui sont traqués et catalogués par une armée de scientifiques au service de l'empereur. De nombreux documents astronomiques ont ainsi été produits sur plusieurs millénaires, conservés ou récemment redécouverts par l’archéologie. C’est le cas notamment de la plus ancienne carte d’étoiles connue au Monde conçue il y a plus de 1200 et préservée dans un monastère bouddhique de la route de la Soie.
Avec la présentation de ces documents, on retracera les étapes, les instruments et les concepts qui ont mené l'astronomie chinoise ancienne à de nombreuses découvertes du ciel transitoire, à des époques où l’Europe n’envisageait encore le Ciel que comme une voute céleste fixe, éternelle et immuable. Avec ce recul de l’histoire, la mission franco-chinoise SVOM, qui va détecter et cataloguer les plus puissants phénomènes célestes variables, apparait aujourd'hui comme une continuation logique dans laquelle la France rejoint symboliquement la Chine dans la préoccupation du ciel transitoire. Local contact: Jean-Marc BONNET-BIDAUD; organization: Frédéric GALLIANO |
Tuesday November 12 10:00 | Joel ONG (Institute for Astronomy, University of Hawaii at Manoa)
New Views into Stellar Rotation from Asteroseismology
[click here for abstract] Asteroseismology — the analysis and interpretation of stellar oscillations — remains the only means by which we may directly inspect the properties of stellar interiors. I will describe new theoretical developments regarding the interpretation of asteroseismic rotational signatures in a particular class of variable stars — red-giant solar-like oscillators. While waves in most variable stars propagate in a single mode cavity, I formulate a description of multicavity oscillations in these red giants by way of a physical analogy where they behave as "acoustic molecular orbitals". I describe two recent observational results which this formalism has helped us to interpret: 1. the detection of engulfment signatures in evolved red giants, and 2. direct constraints on the misalignment angle between the rotational axis of the core and of the envelope, in the central star of a spin-orbit-misaligned planetary system. Local contact: Rafael GARCIA; organization: Frédéric GALLIANO |
Tuesday November 19 10:00 | Postdoc seminar / séminaire postdoc Jose Ignacio "Nacho" ANEZ LOPEZ (LFEMI)
Signatures of magnetic braking in Class 0 protostars ? Exploring the gas kinematics in magnetized models of low-mass star formation
[click here for abstract] The role of magnetic braking in regulating gravitational collapse and circumstellar disk during the main accretion phase, is an open question. While only indirect evidence was found from observational work, such as compact disk sizes and the launching of high-velocity collimated jets, we aim at more direct tests of the magnetic braking in observations. The study of polarized dust emission as a tracer of the magnetic field and molecular line emission as a tracer of gas kinematics in young protostars can provide valuable information for understanding how the presence of the magnetic field affects the accretion process.
In the present work, we have used both non-ideal MHD models and synthetic observations from the radiative transfer of protostellar formation to put constraints on the magnetically-regulated disk formation scenario. We use our model synthetic observations to identify possible direct signatures of the magnetic braking from the maps of the molecular gas emission. By comparing the specific angular momentum of two similar models that differ in magnetic flux, we see that the more magnetized model shows a higher angular momentum redistribution above 1000 au. In addition, we have tested the methods typically used to infer the specific angular momentum from an observational point of view. We have found possible observational evidence of magnetic braking in the kinematics of the C18O(2-1) molecule, such as a flattening of the radial profile of specific angular momentum for radii smaller than 1000 au for the more magnetized model similar to the characteristics found in observational work. On the other hand, in this study we show that the maximum velocity computed in the equatorial plane, which is traditionally used as an approximation of the rotational velocity, may overestimate the rotational velocity, probably due to contamination from radial motions. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday November 26 | Special event / Événement spécial Visite de l'HCERES (AIM) / no seminar |
Tuesday December 3 10:00 | Stefano CAMERA (University of Turin)
Synergic cosmology across the spectrum
[click here for abstract] In my talk, I shall review the main research projects I'm involved in, which all revolve around the added value of cross-correlations between various cosmological observables, as well as among cosmological and astrophysical observables, to shed new light onto pressing open questions in cosmology. In particular, I shall touch upon the possibility of detecting relativistic effects on cosmological scales - which will allow us to deepen our understanding of dark energy and modified gravity -, novel approaches to probe primordial non-Gaussianity, and the use of cosmological data to filter out astrophysical processes in studies of indirect detection of particle dark matter signatures. All this in the view of the new generation of cosmological experiments across the electromagnetic spectrum, like the SKA Observatory in the radio band, or the Euclid satellite at optical/near-infrared wavelengths. Local contact: Martin KILBINGER; organization: Fabian HERVAS-PETERS |
Tuesday December 10 | Special event / Événement spécial Visite de l'HCERES (Irfu) / no seminar |
Tuesday December 17 10:00 | Jean BALLET, Anne DECOURCHELLE, Gabriel PRATT et al. (LEPCHE)
Les 25 ans d'XMM
[click here for abstract] Lancé le 10 décembre 1999, le satellite XMM-Newton d'observation en rayons X fêtera ses 25 ans d'opération et d'exploitation scientifique, et une moisson de résultats scientifiques dans de nombreux domaines. Nous vous invitons mardi 17 septembre 2024 à un séminaire d'anniversaire de la mission XMM-Newton, pierre angulaire du programme Horizon 2000 de l'Agence Spatiale Européenne. Nous retracerons à plusieurs voix l'implication du DAp-AIM dans la réalisation et l'exploitation des données de XMM-Newton, et vous présenterons une sélection de résultats scientifiques marquants. Local contact: Anne DECOURCHELLE; organization: Pierre-Antoine FRUGIER |
2023 | |
Tuesday January 10 10:00 | Stéphane AUNE, Jean-Charles CUILLANDRE et Pierre ASTIER (CEA/SEDI, CEA/DAp et LPNHE)
20 years of MegaCam scientific operations on the Canada-France-Hawaii Telescope
[click here for abstract] Over its history CFHT has helped build or hosted dozens of instruments, operating from ultraviolet to mid-infrared wavelengths, attuned to Maunakea’s renowned observing conditions. One instrument, though, eclipses them all – MegaCam. It is in fact hard to imagine CFHT’s success today without the decisions made two decades ago to build what was then the largest digital focal plane in the world. MegaCam took engineering techniques to closely mount CCDs into a single camera to a whole new level. With its 1 degree field of view, MegaCam was able to tile the sky with images, creating rich and precise datasets on enormous scales that could be mined by the entire scientific community for decades. To date MegaCam has led to more peer reviewed science publications than all other instruments used at CFHT combined. It has been used to tune the model of Dark Energy and map vast regions of Dark Matter, unveil faint wisps of stars flung from interacting galaxies, reveal hundreds of free floating planets in star forming regions, and is currently directly contributing to a Stage IV dark energy measurement by providing the key ground-based photometry for the ESA Euclid space mission to derive photometric redshifts of hundreds of millions of galaxies over the northern sky. All of this is part of a revolution in wide field high-resolution optical imaging that CFHT pioneered for many years. Three speakers will offer a complete overview from technical aspects to the most impactful scientific result over these past two decades:
Local contact: Pierre-Antoine FRUGIER; organization: Pierre-Antoine FRUGIER |
Tuesday January 17 10:00 | Ludovic PETITDEMANGE (LRA/LERMA)
Dynamo action and angular momentum transport in simulated stellar radiative zones
[click here for abstract] The evolution of a star is influenced by its internal rotation dynamics through transport and mixing mechanisms, which are poorly understood. Magnetic fields can play a role in transporting angular momentum and chemical elements, but the origin of magnetism in radiative stellar layers is unclear. Using global numerical simulations, we identify a subcritical transition to turbulence due to the generation of a magnetic dynamo. Our results have many of the properties of the theoretically-proposed Tayler-Spruit dynamo mechanism, which strongly enhances transport of angular momentum in radiative zones. It generates deep toroidal fields that are screened by the stellar outer layers. This mechanism could produce strong magnetic fields inside radiative stars, without an observable field on their surface. Magnetic fields generated by dynamo action appear as a process to trigger turbulence in stellar interiors. Depending on the parameters or initial conditions, we report different dynamo branches that could explain stellar magnetism and the rotation profiles observed for stars having a thick radiative envelope. Local contact: Raphaël RAYNAUD; organization: Raphaël RAYNAUD |
Tuesday January 24 10:00 | [TBA] |
Tuesday January 31 10:00 | Cancelled / séminaire annulé Julien AUBERT (IPGP)
Variations géomagnétiques rapides: un nouveau message émis par le noyau de la Terre
[click here for abstract] Le signal géomagnétique est une source riche d’informations sur la structure, la dynamique interne et l’histoire de notre planète. La production du champ magnétique Terrestre par effet dynamo dans le noyau externe implique une large disparité d’échelle spatiales et plus spécifiquement temporelles, s’étalant sur une gamme allant de l’année au milliard d’années. Depuis la mise en place d’observatoires magnétiques à la surface émergée de la Terre, l’attention s’est portée sur l’explication des variations à l’échelle du siècle, qui sont liées aux mouvements de convection dans le noyau. Depuis une vingtaine d’années, une couverture satellitaire globale et continue a cependant mis en évidence des variations de l’année à la dizaine d’années, dont l’origine est débattue. Ces nouvelles données ouvrent une fenêtre sur des phénomènes magnétohydrodynamiques rapides, de nature ondulatoire, en interaction avec la convection lente dans le noyau. Dans cet exposé, je présenterai les défis posés par la simulation conjointe des deux phénomènes ainsi que les avancées récentes et applications géophysiques potentielles. Local contact: Sacha BRUN; organization: Frédéric GALLIANO |
Tuesday February 7 10:00 | [TBA] |
Tuesday February 14 | Special event / Événement spécial |
Tuesday February 21 | Vacations / Vacances Vacances d'hiver |
Tuesday February 28 | Vacations / Vacances Vacances d'hiver |
Tuesday March 7 10:00 | Cancelled / séminaire annulé Stefano CAMERA (Università degli Studi di Torino)
Cosmology with the SKA Observatory and its Precursors/Pathfinders
[click here for abstract] In this talk, I shall review the most peculiar aspects of cosmology in the radio band, with a special focus on the SKA Observatory (SKAO). I shall present the main radio probes that can be exploited for late-time cosmology: continuum and 21-cm line galaxy surveys, neutral hydrogen intensity mapping, and weak lensing cosmic shear at radio frequencies. Furthermore, I shall present the most recent analyses of actual data from SKAO's pathfinders and precursors. Moreover, I shall discuss the added value of multi-wavelength synergies, presenting some show-case example of the power of radio-optical cross-correlations to test the foundations of the concordance cosmological model, such as the nature of dark matter and dark energy, or tests of inflation and gravity. Local contact: Denise LANZIERI; organization: Denise LANZIERI |
Tuesday March 14 10:00 | Special seminar / séminaire exceptionnel Marie GUÉGUEN (Université de Rennes)
Cosmology: a tension within code comparisons
[click here for abstract] Code comparisons in cosmology are often performed with the underlying objective of identifying predictions upon which different codes converge that can be interpreted as robust, free of artifacts, predictions. Such an objective assumes that code comparisons can be constructed in such a way that the two notions of convergence and of robustness collapse. But, in order to achieve such a goal, code comparisons of structure formation have to meet an important epistemic challenge: that of constructing their codes ensemble on the basis of codes that are as independent as possible, but also comparable. In this talk, I show that enforcing the latter often amounts to multiplying common idealizations that hinder the achievement of the former, and thus leads to code comparisons that include many unscrutinized sources of artefacts possibly similarly distorting the predictions of the model. As a result, I argue that in context of high uncertainties where the domain of verification and validation of simulations has shrunk to code comparisons, code comparisons are better and actually very efficient as exploratory tools, both for getting insights into the physics implemented and for breaking the epistemic opacity of numerical simulations. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday March 21 10:00 | Cancelled / séminaire annulé Francisca KEMPER (Institute of Space Sciences (ICE-CSIC) / ICREA / IEEC, Spain)
The interstellar dust reservoir in galaxies
[click here for abstract] The evolution of interstellar dust reservoirs, and the evolution of galaxies themselves go hand-in-hand, as the presence of dust alters
evolutionary drivers, such as the interstellar radiation field and the star formation history, while at the same time, the dust is being formed and altered by processes taking place in galaxies. However, far-infrared and submillimeter studies have revealed enormous dust masses at high redshifts that are difficult to explain with dust production from evolved stars (the so-called "dust budget problem"), while in the nearby universe there is also a significant mismatch between the dust production rate and the dust mass observed in the interstellar medium of galaxies. I will go over some possible explanations in an attempt to find a way forward towards a solution to this seeming discrepancy. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday March 28 | Special event / Événement spécial |
Tuesday April 4 10:00 | Andrei IGOSHEV (University of Leeds)
Magneto-thermal evolution of neutron stars
[click here for abstract] We perform first three-dimensional simulations of the magneto-thermal evolution using a spectral MHD code for crust confined magnetic field configurations. Our results show that presence of strong toroidal magnetic field in magnetars is necessary to explain their quiescent thermal emission, in particular a formation of a single hot spot. Using our thermal maps we are able to explain light curves of 10 out of 19 magnetars in quiescence. In the case of the central compact objects, we test the configuration of magnetic field formed as a result of stochastic dynamo. Such a magnetic field consists of multiple randomly orientated loops of magnetic field. Surface thermal map is becoming patchy and includes multiple hot and cold regions which are always observed simultaneously. The global dipolar field slowly formed as a result of the Hall and Ohmic evolution. In our simulations we see 5-10% pulsed fraction and difference of two times in temperature between hot and cold regions typical for observations of the central compact objects. We also study off-centred dipole configurations and found that they decay over time. Local contact: Raphaël RAYNAUD; organization: Frédéric GALLIANO |
Tuesday April 11 10:00 | Anne VERHAMME (Université de Genève)
Searching for the sources of Cosmic Reionisation
[click here for abstract] Over the past 5 years, we have made tremendous progress on both direct detections of the escape of ionizing radiation from galaxies, over a broad range of redshifts (and instruments), and the tests and validations of indirect probes of the escape of ionizing radiation from galaxies, both from observations and simulations. I will review these recent achievements, and describe the next steps to understand the nature of the sources of reionisation. Local contact: Vianney LEBOUTEILLER; organization: Frédéric GALLIANO |
Tuesday April 18 10:00 | Judith IRWIN (Queen's University, Canada)
CHANG-ES — Past and Future
[click here for abstract] CHANG-ES (Continuum Halos in Nearby Galaxies — an EVLA Survey) is a project to observe 35 nearby galaxies that are edge-on to the line of sight to focus on their radio halos and the disk-halo connection. Wide-band VLA observations at L-band (1.5 GHz) and C-band (6.0 GHz) have provided opportunities to study in-band spectral indices, and observations in all four Stokes parameters with Rotation Measure Synthesis has led to a new understanding of the structure of kpc-scale magnetic fields in disk galaxies. This talk will highlight some of the results of the project and look to the future, as newly completed S-band (3.0 GHz) observations have filled in the L-band to C-band gap and led to the widest contiguous frequency coverage yet seen for galaxies. Local contact: Suzanne MADDEN; organization: Frédéric GALLIANO |
Tuesday April 25 | Vacations / Vacances Vacances de printemps |
Tuesday May 2 | Vacations / Vacances Vacances de printemps |
Tuesday May 9 10:00 | [TBA] |
Tuesday May 16 10:00 | Special seminar / séminaire exceptionnel Vianney LEBOUTEILLER (LFEMI)
Soft-Skilling in Fundamental Research
[click here for abstract] Artificial intelligence (AI) holds more and more importance in our lives and in our work. While AI undeniably provides a smart and useful companion, the current debates of whether it may replace us altogether in our tasks highlights the role and importance of social interactions and emotions in the work environment at large.
In this non-astrophysics seminar, I will present a recent study whose goal is to identify socio-professional (a.k.a. transversal, transferable, or generally "soft") skills that are critical in the transformation and innovation of companies/industries. As it turns out, most of these skills are actually acquired or at least strengthened throughout a career in fundamental research, including during the PhD. This is not surprising as transformation, innovation, but also breakthroughs, creativity etc... are common motivations in both worlds in which we seek answers to questions but we also seek questions themselves, within a complex environment and network of people. Many difficulties arise when dealing with soft skills, however: identifying them, acquiring and/or realizing they have been acquired, improving them, measuring them, making them valuable, and convincing other people they have been acquired. All in all, while most soft skills are well-known, the process of sorting, grouping, ranking them is necessary to set reference frameworks that can be acknowledged by most people. The purpose of this talk is to describe what soft skills are, how they are an integral part of research, and preliminary thoughts on how they can be applied/converted to non-academic world. Local contact: Vianney LEBOUTEILLER; organization: Frédéric GALLIANO |
Tuesday May 23 10:00 | Cancelled / séminaire annulé James DUNLOP (University of Edinburgh)
Galaxies in the young Universe
[click here for abstract] I will discuss recent breakthroughs in our understanding of galaxy evolution in the first billion years, including the impact of early galaxy growth on the (hydrogen) reionisation of the IGM. I will focus primarily on recent observational breakthroughs, especially with ALMA, VISTA, Subaru,
HST and now (in particular) with the James Webb Space Telescope (JWST), but will also briefly consider the connections and tensions with theoretical predictions. I will endeavour to provide a balanced overview of this rapidly moving field, while highlighting recent advances that have been led from Edinburgh. Finally, I will consider the prospects for further improvement in our knowledge of early galaxy formation over the coming years. Local contact: Carlos GÓMEZ-GUIJARRO; organization: Carlos GÓMEZ-GUIJARRO |
Tuesday May 30 10:00 | Cancelled / séminaire annulé Stefanie WALCH-GASSNER (University of Köln)
The impact of stellar feedback on different scales and galactic environments
[click here for abstract] Stellar feedback refers to the processes by which massive stars release energy, radiation and material into their surroundings, influencing the structure and evolution of the galaxies in which they reside. Understanding the impact of stellar feedback on different galactic environments is crucial for developing a comprehensive picture of galaxy formation and evolution. In this context, different galactic environments refer to regions within a galaxy that differ in their physical conditions, such as the average gas density, temperature, or metallicity.
We study the respective impact of stellar winds, ionizing radiation, and supernovae in modern simulations of the multi-phase interstellar medium in parts of galaxies within the SILCC project, which I will present in this talk. From these galactic scale simulations we find that ionizing radiation is the most important factor in regulating the star formation rate, while supernova over-pressure the gas substantially, thus driving a galactic outflow. Local contact: Suzanne MADDEN; organization: Frédéric GALLIANO |
Tuesday June 6 10:00 | Postdoc seminar / séminaire postdoc Carlos GÓMEZ GUIJARRO (LCEG)
Understanding the role of compact star formation in galaxy evolution with ALMA and JWST
[click here for abstract] Massive elliptical galaxies in the local universe appear to have their high-redshift analogs in the form of extremely compact quiescent galaxies. Therefore, it seems that compact star formation appears to play a pivotal role in the evolutionary pathways of massive galaxies across cosmic history. However, it remains to be understood what this role is in the broader picture set by the main sequence and the scaling relations in galaxy evolution. From an ALMA survey at 1.1mm, we reveal that compact star formation appears to be the norm in massive star-forming galaxies, and sizes as extended as typical star-forming stellar disks are rare. A population of galaxies with modest star formation rates, but which exhibit extremely compact star formation with starburst-like depletion timescales unveils. Compact star formation appears as a physical driver of depletion timescales, gas fractions, and dust temperatures. Gas and star formation compression seems to be a mechanism that allows to hold their star formation rate even when their gas fractions are low and they are presumably on the way to quiescence. Another population of galaxies missed in the deep optical surveys but bright at far-IR/mm wavelengths unveils thanks to recent JWST observations. We present a study investigating the drivers of dust attenuation in massive galaxies in the JWST-era, showing how the stellar mass and morphology plays an important role, with evidence for more compact stellar profiles resulting in the obscuration of galaxies. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday June 13 10:00 | Postdoc seminar / séminaire postdoc Ugo LEBREUILLY (LMPA)
Gas and dust evolution during the formation of protoplanetary disks
[click here for abstract] Protoplanetary disks are the consequence of angular momentum conservation during the protostellar collapse. Their formation is a complex process which includes numerous physical effects (non-ideal MHD, stellar feedback, gas and dust interactions, turbulence…). In this seminar, I will
present our recent works to better understand the formation of these disks. In the first part of the talk, I will focus on their gas content. I will show how modelling simultaneously the large scales of star forming regions and the small scales of protoplanetary disks allows us to constrain the statistical properties (mass, radius, temperature…) of these disks. The second part of the talk will be dedicated to the study of dust evolution. In particular, I will stress the consequences of this process not only for the formation of disks, but also for the formation of planets. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday June 20 | Special event / Événement spécial Semaine de la SF2A |
Tuesday June 27 10:00 | Julien AUBERT (IPGP)
Variations géomagnétiques rapides: un nouveau message émis par le noyau de la Terre
[click here for abstract] Le signal géomagnétique est une source riche d’informations sur la structure, la dynamique interne et l’histoire de notre planète. La production du champ magnétique Terrestre par effet dynamo dans le noyau externe implique une large disparité d’échelle spatiales et plus spécifiquement temporelles, s’étalant sur une gamme allant de l’année au milliard d’années. Depuis la mise en place d’observatoires magnétiques à la surface émergée de la Terre, l’attention s’est portée sur l’explication des variations à l’échelle du siècle, qui sont liées aux mouvements de convection dans le noyau. Depuis une vingtaine d’années, une couverture satellitaire globale et continue a cependant mis en évidence des variations de l’année à la dizaine d’années, dont l’origine est débattue. Ces nouvelles données ouvrent une fenêtre sur des phénomènes magnétohydrodynamiques rapides, de nature ondulatoire, en interaction avec la convection lente dans le noyau. Dans cet exposé, je présenterai les défis posés par la simulation conjointe des deux phénomènes ainsi que les avancées récentes et applications géophysiques potentielles. Local contact: Sacha BRUN; organization: Frédéric GALLIANO |
Thursday June 29 10:00 | Julien DE WIT (Department of Earth, Atmospheric and Planetary Science, MIT, USA)
Robustly Characterizing Exoplanets in a New Era of High-Precision Transit Measurements
[click here for abstract] With a new-generation of great observatories coming online this decade, unprecedented insights into exoplanets will soon be within reach. Observatories such as the James Webb Space Telescope (JWST) notably enable the study of atmospheres around terrestrial exoplanets and can reveal tri-dimensional structures in the atmospheres of their larger counterparts. Robustly leveraging new observations to reach such achievements will however require extra care as the models currently used may not be up to par with their precision.
During this presentation, I will introduce work done by MIT’s Disruptive Planets group and collaborators towards supporting the robust in-depth characterization of exoplanets. I will specifically discuss how not accounting for the true shape of a planet can lead to a misinterpretation of its interior properties as well as atmospheric structure; how the current state of our understanding of light-matter interactions can similarly affect our interpretation of planetary spectra and thus inferences regarding their atmospheric properties; and how the current state of emission spectrum models for stars may even prevent from disentangling between the contribution of a planet and its host star, to start with. I will also present possible ways to address these challenges. I will end with a step-by-step roadmap to the robust characterization of temperate terrestrial planets with JWST, which includes habitability assessment. Local contact: Elsa DUCROT; organization: Frédéric GALLIANO |
Tuesday July 4 | Vacations / Vacances Coupure estivale |
Tuesday September 5 10:00 | Postdoc seminar / séminaire postdoc Lucie BAUMONT (LCS)
Galaxy Cluster Cosmology with fgas
[click here for abstract] The current Standard Model of Cosmology has successfully explained many phenomena, but it predicts that the majority of the Universe consists of dark matter and dark energy, whose properties are poorly understood. Because huge volumes collapse to form galaxy clusters, the largest known gravitationally bound structures, they are an ideal laboratory to study the Dark Universe. In fact, the ratio of baryonic matter to total matter in a massive cluster, fgas, can be considered representative of the matter content of the Universe as a whole. Measurements of fgas from the heaviest, dynamically relaxed galaxy clusters place powerful constraints on cosmological parameters as well as the dark energy equation of state. I will discuss constraints derived from fgas measurements using a multi-wavelength set of X-ray and optical data and provide outlook on the future of this measurement in the age of precision cosmology. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday September 12 10:00 | Alexander MOISEEV (NASA/GSFC and University of Maryland)
New Mission Concept: Compton Telescope with Coded Aperture Mask, and its Science Perspectives
[click here for abstract] The Galactic Explorer with a Coded Aperture Mask Compton Telescope (GECCO) is a novel Explorer-class concept for a next-generation telescope covering the poorly explored hard X-ray and soft gamma-ray energies. This concept builds upon the heritage of past and current missions, improving sensitivity and, very importantly, angular resolution. GECCO uses the combined Coded Aperture Mask and Compton telescope techniques to employ the benefits of both: superior angular resolution provided by the deployable Coded Aperture Mask, and good background rejection and wide field-of-view (FoV) provided by the Compton telescope. It is being developed at NASA/GSFC in collaboration with other US and foreign institutions. GECCO observations will extend arcminute angular resolution to high-energy images of the Galactic plane, combining the
spectral capabilities of INTEGRAL/IBIS and the x-ray imaging of NuSTAR and eROSITA, and will make a bridge to the Fermi-LAT observations, enabling a broad potential for discoveries in the MeV γ-ray sky.
With the unprecedented angular resolution of the coded mask telescope combined with the sensitive, wide FoV Compton telescope, GECCO will focus on two main science objectives:
The GECCO design is based on the novel CZT Imaging calorimeter, which serves as a standalone Compton telescope and as a focal plane detector for the Coded Mask. It also is a powerful tool to measure the γ-radiation polarization. GECCO’s octagon-shaped active shield also serves as a powerful all-sky detector of gamma-ray bursts, prompting the instrument to slew towards the burst direction and localize it with the Coded Aperture’s arcminute accuracy. GECCO will operate in the 100 keV - 10 MeV energy range, with energy resolution of ~ 1% from 0.5 - 5 MeV. The Coded Aperture Mask provides the angular resolution of ∼1 arcmin with a 2 × 2 deg2 fully coded field-of-view, while the Compton telescope provides the angular resolution of 3◦ − 6◦ with a 60 × 60 deg2 field-of-view. The 3σ, 106 s sensitivity is expected to be about 10-5 MeV cm-2 s-1 over the entire energy range. Primary mode of observation is fixed pointing, with extended exposure of the regions of interest. However, as a standalone Compton telescope with wide FoV, Imaging Calorimeter will simultaneously provide wide-area sky exploration, significantly broadening GECCO’s observational scope. Local contact: Philippe LAURENT; organization: Frédéric GALLIANO |
Tuesday September 19 10:00 | Arjen VAN DER WEL (Ghent University, Belgium)
Galaxy Evolution from z=3 to the Present Day: Recent Insights from JWST and VLT surveys
[click here for abstract] Thanks to an abundance of excellent observational data the evolution of the population of galaxies in terms of its stellar mass function, the distribution of star-formation across galaxies and their structural properties is known with good precision. The challenge we face, though, is to decipher the evolutionary paths of individual galaxies. Two roads to achieving this goal are 1) to reconstruct star-formation histories of individual galaxies through detailed modeling of high-quality spectra, and 2) attempt to define 'rules' for galaxy evolution that tell us how the collection of individual galaxies must evolve so that the population properties are reproduced. I will describe our recent progress along these lines, enabled by high-quality data from VLT spectroscopy of z~1 galaxies (the LEGA-C survey) and high-quality imaging data from HST (CANDELS) and JWST (CEERS). Local contact: Emanuele DADDI; organization: Carlos GÓMEZ GUIJARRO |
Tuesday September 26 10:00 | Postdoc seminar / séminaire postdoc Adam FINLEY (LDE3)
Studying the whole Sun: from small-scale heating to large-scale dynamics
[click here for abstract] The Sun’s large-scale magnetic field undergoes periodic reversals due to dynamo-action in the solar interior, through which the Sun’s magnetic field regenerates. The emergence of new magnetic field at the solar surface, after buoyantly rising through the convection zone, is clearly
visible due to the formation of dark spots (sunspots). However, current models of the solar dynamo are unable to self-consistently capture the formation of sunspots, due to the range of pressure scale heights needed to include the photosphere. Thus, dynamo models remain disconnected from sunspot observations. The cyclic evolution of the Sun’s magnetic field also has a clear impact on the structure of the solar atmosphere and outflowing wind above. Similarly, linking the evolution of different scales, from the buffeting of convective motions in the photosphere to the dissipation of Alfven waves in the solar wind. Modern models of the Sun, therefore, require the combination of expertise from a range of interconnected subject areas. In this talk, I will highlight some of the recent work from the WholeSun ERC Synergy grant (https://wholesun.eu), which
brings together expertise from five different host institutions across Europe. These works range from assessing the observational signatures of toroidal flux generation, to modelling small-scale energy injection at the base of the solar wind, and finally, estimating the large-scale variation in coronal structure and rotation during the solar cycle. Local contact: Barbara PERRI; organization: Carlos GÓMEZ GUIJARRO |
Tuesday October 3 10:00 | Postdoc seminar / séminaire postdoc Lara PANTONI (LFEMI)
Dust millimetre emission in nearby galaxies with NIKA2 (IRAM-30m): major challenges and latest results of the IMEGIN Large Program
[click here for abstract] The millimetre part of the spectrum is one of the least explored parts of a galaxy’s spectral energy distribution (SED), yet it contains emissions from three fundamentally important physical processes. These processes are thermal emission from dust, free-free emission from ionized gas and synchrotron emission from relativistic charged particles moving in the galactic magnetic field. The NIKA2 camera (IRAM-30m telescope), observing at 1.15 mm and 2 mm, provides additional data points for input into the comprehensive SED models and allows us to:
During my presentation, I will focus on the major challenges linked with data processing, uncertainty propagation, and large-scale emission filtering in NIKA2 maps (due to atmosphere removal during the data reduction process). I will show and discuss the latest significant results on NGC891 (Katsioli et al. 2023); NGC4254 (Pantoni et al. in prep.); NGC2976 and NGC2146 (Ejlali et al. in prep.); millimetre morphology (Nersesian et al. in prep.); future perspectives/applications. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Wednesday October 4 14:00 | Joint DAp-DPhP seminar / séminaire DAp-DPhP joint Roland BACON (CRAL)
WST - The Wide Field Spectroscopic Telescope
[click here for abstract] The WST project aim to study and built an innovative 10-m class wide-field spectroscopic survey telescope (WST) in the southern hemisphere with simultaneous operation of a large field-of-view (5 sq. degree) and high multiplex (20,000) multi-object spectrograph facility with both medium and high resolution modes (MOS), and a giant panoramic integral field spectrograph (IFS). The ambitious WST top-level requirements place it far ahead of existing and planned facilities. In just its first 5 years of operation, the MOS will target 250 million galaxies and 25 million stars at medium resolution + 2 million stars at high resolution, and 4 billion spectra with the IFS. WST will achieve transformative results in most areas of astrophysics. The combination of MOS and IFS spectroscopic surveys is one of the key aspects of the project. It is very attractive because of the high complementarity between the two approaches. I will detail this innovative point using the example of the MOS and MUSE surveys performed in the CDFS region. The project aims to be the next major post-ELT project. It is supported by a large consortium of very experienced institutes plus ESO, representing 9 European countries and Australia. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday October 10 | Special event / Événement spécial Séminaire de prospective d'AIM |
Tuesday October 17 10:00 | Postdoc seminar / séminaire postdoc Sudip CHAKRABORTY (LEPCHE)
Unraveling the magnetic origin of dense non-equatorial ultrafast outflows in black hole X-ray binaries
[click here for abstract] Accretion of matter onto black holes often gives rise to outflows in the form of collimated relativistic jets and uncollimated winds. A deeper understanding of the launching mechanisms behind these outflows, manifesting in the form of blue-shifted absorption lines in the X-ray spectrum, can lead to valuable insights towards the behaviour of matter under extreme gravity. While low-velocity winds are considered to be ubiquitous in almost all accreting black holes, winds of relativistic velocities have been detected in a significant fraction of active galactic nuclei (AGN) over the last two decades. Out of the three prevalent wind-driving mechanisms (thermal, magnetic and radiative), these relativistic winds (also called Ultrafast Outflows or UFOs) could be launched by the latter two. However, a comprehensive investigation of the robust UFOs in Galactic black hole X-ray binaries (BHBs) has not yet been conducted in a systematic fashion, leaving a gap in our knowledge of the physics of black hole accretion across the mass range. In this talk, I will highlight our recent work in which we try to bridge this gap for the first time. In this work, we probe the magnetic driving behind the dense, non-equatorial UFOs in four BHBs with the NuSTAR, NICER and other X-ray observatories. We conduct detailed reflection modelling of the broadband X-ray spectra to measure the properties of the accretion disk and a direct MHD modelling of the absorption lines to determine the corresponding properties of the UFOs, thereby demonstrating an essential synergy between the reflection and absorption spectroscopy. The results of our study point towards a magnetic origin of UFOs in BHBs and hint that these low-inclination UFOs are necessarily supplemented with high wind and disk densities in order to be observed with current X-ray instruments. Such magnetically driven winds indicate a remarkable invariance of accretion and ejection processes over the very wide range of black hole masses, from stellar to super-massive. We anticipate our assay to be the gateway to more exhaustive future studies of UFOs in more comprehensive samples of BHBs and further exploration of magnetic wind driving in the JAXA/NASA’s XRISM era. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Friday October 20 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Tommaso RONCONI (SISSA, Trieste, Italy)
Introducing Galapy: a fast API for modelling galaxy SEDs with Bayesian sampling
[click here for abstract] Fostered by upcoming data from new generation observational campaigns, we are about to enter a new era for the study of how galaxies form and evolve. The unprecedented quantity of data that will be collected, from distances only marginally grasped up to now, will require analysis tools designed to target the specific physical peculiarities of the observed sources and handle extremely large datasets. One powerful method to investigate the complex astrophysical processes that govern the properties of galaxies is to model their observed spectral energy distribution (SED) at different stages of evolution and times throughout the history of the Universe.
In this talk, I will introduce GalaPy, a new library for modelling and fitting galactic SEDs from the X-ray to the radio band, as well as the evolution of their components and dust attenuation/reradiation. On the physical side, GalaPy incorporates both empirical and physically-motivated star formation histories, state-of-the-art single stellar population synthesis libraries, a two-component dust model for extinction, an age-dependent energy conservation algorithm to compute dust reradiation, and additional sources of stellar continuum such as synchrotron, nebular/free-free emission and X-ray radiation from low and high mass binary stars. On the computational side, GalaPy implements a hybrid approach that combines the high performance of compiled C++ with the user-friendly flexibility of Python, and exploits an object-oriented design via advanced programming techniques. GalaPy generates models on the fly without relying on templates, thus minimising memory consumption. It exploits fully Bayesian parameter space sampling, which allows for the inference of parameter posteriors and thus facilitates the study of the correlations between the free parameters and the other physical quantities that can be derived from modelling. The API and functions of GalaPy are under continuous development, with planned extensions in the near future. I will showcase the project and present the photometric SED fitting tools already available to users. Local contact: Lara PANTONI; organization: Frédéric GALLIANO |
Tuesday October 24 | Vacations / Vacances Vacances de la Toussaint |
Tuesday October 31 | Vacations / Vacances Vacances de la Toussaint |
Tuesday November 7 10:00 | Postdoc seminar / séminaire postdoc [TBA] |
Tuesday November 14 | Special event / Événement spécial Local meeting |
Tuesday November 21 10:00 | Recent hiree seminar / séminaire arrivant récent Camila CORREA (LCEG)
Journey into the Unknown: Dark Matter, Observations of Galaxies, and the Path Forward
[click here for abstract] The nature of dark matter remains as one of the big unknowns of our time. The general expectation for the coming years is that Euclid, DESI, Rubin LSST, among others, will facilitate the production of wide-field galaxy surveys with exceptionally precise measurements, which will be crucial for unraveling the mysteries surrounding dark matter. We eagerly anticipate that the new observations will reveal deviations from the canonical cold collisionless dark matter paradigm, offering insights into its true nature. However, the key question lingers: will it really happen? What is missing now, that Euclid and others state-of-the-art facilities will change? In this seminar, I will strive to address these questions and review the latest status on dark matter searchers, in order to give you an impression of where we are in the search for dark matter and where we are going.
Throughout the seminar, I will also provide an overview of my work on the nature of dark matter and delve into the pivotal role that cosmological simulations of galaxy formation play in this quest. In the interpretation of data from both current and upcoming state-of-the-art observatories, cosmological simulations have emerged as indispensable tools. Simulations have convinced us of the success of LCDM over large scales, and have given us the capability of breaking the degeneracy driven by baryonic physics and dark matter models. However, can we really trust the outcomes of simulations? with their limited resolution and ad-hoc subgrid prescriptions for galaxy evolution. Maintaining a critical perspective on the observational data we work with and the simulated data we generate daily is crucial for advancing in this field. During the seminar, I will provide updates on the current challenges faced by cosmological simulations and highlight the progress they have achieved. I plan to be as efficient as possible to ensure time for a concluding session that hopefully leaves you with food for thought—an engaging discussion about the future. What steps lie ahead in the development of cosmological simulations? What about on the nature of dark matter? What synergies are needed to be forged between theoretical advancements and observational endeavours? And, importantly, what role will DAp play in this unfolding narrative? Let’s chat more on Tuesday 21 Nov. at 10 am. Local contact: Frédéric BOURNAUD; organization: Carlos GÓMEZ GUIJARRO |
Tuesday November 28 10:00 | Elisa CHISARI (University of Oxford)
A rising tide: galaxy alignments in the Stage IV era
[click here for abstract] A new generation of galaxy surveys is at our doorstep. By mapping billions of galaxies over the sky, they will deliver precision constraints on the cosmological model. The significant gains in constraining power are accompanied by the need to develop more accurate models of galaxy shapes. Several physical effects will come into play that could be neglected or simplified in previous analyses. I will discuss the constraining power of upcoming surveys, focusing mostly on Rubin Observatory, and the modelling challenges they face. Amongst such challenges, I will focus mostly on the “intrinsic alignments” of galaxies: alignments between their shapes that are likely to arise from tidal interactions between them. I will describe some new modelling strategies that could help reduce their impact on cosmological constraints. Finally, I will present some opportunities that arise for using intrinsic alignments themselves as a probe of cosmology and galaxy evolution. Local contact: Martin KILBINGER; organization: Fabian HERVAS PETERS |
Tuesday December 5 10:00 | Recent hiree seminar / séminaire arrivant récent Barbara PERRI (LDE3)
Space weather in the era of Solar Orbiter and rising solar activity
[click here for abstract] Space weather is about connecting the Sun to the Earth, and being able to anticipate the most extreme solar events and their impact on our technology and health. It becomes even more challenging during periods of maximum solar activity, which happen every 11 years due to the solar dynamo, and which is currently happening right now (maximum peak estimated in 2025). Luckily, the current conjecture of space observatories dedicated to the Sun-Earth chain is very complimentary, with new missions like Solar Orbiter providing unique and useful insight.
I will present here some of my contributions to space weather research at DAp, focusing especially on the impact of solar activity and how Solar Orbiter data can help with this challenging regime. I will first explain how far-side and out of the ecliptic data gaps filled with Solar Orbiter will influence solar wind simulations. Then, I will show how the modulation of solar activity in the heliosphere will influence the propagation of transients such as CMEs (Coronal Mass Ejections) or cosmic rays. Finally, I will extend my research to the subject of exo-space weather, and discuss how the dynamo-wind coupling may influence other stars and their environment. Local contact: Barbara PERRI; organization: Frédéric GALLIANO |
Wednesday December 6 10:00 | Ute LISENFELD (University of Granada)
Molecular gas in galaxies in compact groups
[click here for abstract] Galaxies in compact groups live in an environment where constant interactions take place, both through tidal and through collisional processes. They are are therefore ideal objects to study the influence of the environment on galaxy properties and evolution, in particular the quenching of star formation.
The atomic hydrogen is extremely affected by this environment, with high deficiencies in many cases, whereas the molecular gas content is on average relatively normal in most galaxies. However, the properties of the molecular gas are drastically different if one selects those galaxies, based on their mid-infrared colours from the Spitzer and WISE satallites, that are in transitioning phase from active to quiescent which have have a considerably lower molecular-to-stellar mass and star formation efficiency. In my talk I will present result form observations of the molecular gas and star formation in galaxies in compact groups, both from single dish and interferometric observations, that show indications that in many cases the molecular is highly perturbed (and therefore unable to form stars) in compact groups. Local contact: Suzanne MADDEN; organization: Frédéric GALLIANO |
Tuesday December 12 10:00 | Stefano ANDREON (INAF-OA Brera, Milan, Italy)
First massive galaxy clusters emerging from the cosmic web at z~2
[click here for abstract] In this talk I report upon our results on the intracluster medium (ICM) of two clusters at the time when first clusters start to emerge from the cosmic web, z~2. Results are derived from new, high resolution, deep SZ and X-ray data providing us with the measurement of the two most distant resolved pressure profiles. IDCSJ1426 cluster at z=1.75 has a core whose properties are not far from the final stage, while the remaining part of the cluster is experiencing a sizable gas, heat and entropy transfer. JKCS041 at z=1.80 is caught just after a major merger event as evidenced by its SZ-X-ray peak offset, its low central pressure, and its low Compton-Y parameter compared to its WL mass. Comparison with plausible descendents shows that its ICM will experience major changes at all radii. Local contact: Jean-Charles CUILLANDRE; organization: Carlos GÓMEZ GUIJARRO |
2022 | |
Tuesday February 1 10:00 | Pascal TREMBLIN (Maison de la Simulation)
Non-ideal self-gravity and cosmology: the importance of correlations in the dynamics of the large-scale structures of the Universe
[click here for abstract] Inspired by the statistical mechanics of an ensemble of interacting particles (BBGKY hierarchy), we propose to account for small-scale inhomogeneities in self-gravitating astrophysical fluids by deriving a non-ideal Virial theorem and non-ideal Navier-Stokes equations using a decomposition of the gravitational force into a near- and far-field component. These equations involve the pair radial distribution function (similar to the two-point correlation function), similarly to the interaction energy and equation of state in liquids. Small-scale correlations lead to a non-ideal amplification of the gravitational interaction energy, whose omission leads to a missing mass problem, e.g., in galaxies and galaxy clusters. We also propose an extension of the Friedmann equations in the non-ideal regime. We estimate the non-ideal amplification factor of the gravitational interaction energy of the baryons to lie between 5 and 20, potentially explaining the observed value of the Hubble parameter. Within this framework, the acceleration of the expansion emerges naturally because of the increasing number of sub-structures induced by gravitational collapse, which increases their contribution to the total gravitational energy. A simple estimate predicts a non-ideal deceleration parameter qni~-1; this is potentially the first determination of the observed value based on an intuitively physical argument. We suggest that correlations and gravitational interactions could produce a transition to a viscous regime that can lead to flat rotation curves. This transition could also explain the dichotomy between (Keplerian) LSB elliptical galaxy and (non-Keplerian) spiral galaxy rotation profiles. Overall, our results demonstrate that non-ideal effects induced by inhomogeneities must be taken into account in order to properly determine the gravitational dynamics of galaxies and the larger scale universe. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday February 8 10:00 | Special seminar / séminaire exceptionnel Ingo WALDMANN (UCL)
Deep learning in exoplanet characterisation
[click here for abstract] The use of machine and deep learning is prevalent in many fields of science and industry and is now becoming more widespread in extrasolar planet and solar system sciences. Deep learning holds many potential advantages when it comes to modelling highly non-linear data, as well as speed improvements when compared to traditional analysis and modelling techniques. However, their often ‘black box’ nature and unintuitive decision processes, are a key hurdle to their broader adoption. In this seminar, I will give an overview of deep learning approaches used in exoplanet characterisation and discuss our recent work on developing Explainable AI (XAI) approaches. XAI is a rapidly developing field in machine learning and aims to make ‘black box’ models interpretable. By understanding how different neural net architectures learn to interpret atmospheric spectra, we can derive more robust prediction uncertainties as well as map information content as function of wavelength. As data and model complexities are bound to increase dramatically with the advent of JWST and ELT measurements, robust and interpretable deep learning models will become valuable tools in our data analysis repertoire. Local contact: Frédéric GALLIANO; organization: Frédéric GALLIANO |
Tuesday February 22 | Vacations / Vacances Vacances d'hiver |
Tuesday March 8 10:00 | Cancelled / séminaire annulé Leonardo TESTI (DAp)
Protoplanetary disks and the dawn of planets
[click here for abstract] In the classical picture of star and planet formation, disks are expected to form as a natural consequence of core collapse to form stars. Disks are then expected to mediate the extraction of excess angular momentum during the stellar accretion phase, and to be the locus of planet formation at later times. Reality is obviously much more complicated than this one line overview: disk properties “at birth” are a complex function of the star formation environment, the problem of transport in disks is far from being fully understood, as are the initial condition and timeline for planet formation. In this talk I will discuss some of these problems, mostly focusing on the successes and limitations of our understanding of the properties of individual disks and the global evolution of disk populations. I will discuss the current evidence for early planet formation in protoplanetary disks, and the open questions related to effect of the star formation environment across the Galaxy on disk properties and evolution, which likely also affect the planet formation process. Local contact: Matteo BUGLI; organization: Matteo BUGLI |
Tuesday March 22 10:00 | Benjamin WEHMEYER (CSFK, Budapest)
Galactic Chemical Evolution of rapid neutron capture process elements using special, rare classes of supernovae, and of short lived radioisotopes
[click here for abstract] The origin of the heaviest elements is still a matter of debate. For the rapid neutron capture process (r-process), multiple sites have been proposed, e.g., neutron star mergers and (sub-classes) of supernovae (e.g., magnetorotationally driven supernovae). R-process elements have been measured in a large fraction of metal-poor stars. Galactic archaeology studies show that the r-process abundances among these stars vary by over 2 orders of magnitude. On the other hand, abundances in stars with solar-like metallicity do not differ greatly. This leads to two major open questions:
Local contact: Jérôme GUILET; organization: Matteo BUGLI |
Tuesday April 5 10:00 | Barbara OLMI (INAF, Italy)
Modeling Pulsar Wind Nebulae through their evolutionary phases
[click here for abstract] Pulsar wind nebulae are fascinating systems, powered by the central rotating compact star, emanating a wind in the form of a relativistic, magnetized, and cold plasma that fills the nebula. They are visible as bright non-thermal sources in a very broad range of energies, from radio to gamma-rays. Observed morphologies vary with the evolutionary phase, with middle-aged and old systems strongly affected by the interaction with the ambient medium. Modeling of these sources requires some carefulness when going through the various phases, with a comprehensive description still lacking.
Pulsar wind nebulae had been for a long time thought to contribute substantially to the positron excess in the CR spectrum at Earth -- potentially being the primary sources. In the last years, numerous evidence for efficient particle leakage by aged nebulae had been collected, showing up as quasi-monochromatic misaligned jets at X-rays in some cases, or in the form of extended TeV halos in others, reanimating somehow the interest in this class of objects. Here I will review our present knowledge of pulsar wind nebulae models through their different ages. Local contact: Matteo BUGLI; organization: Matteo BUGLI |
Tuesday April 19 10:00 | Sacha BRUN et Olivier LIMOUSIN (DAp)
Solar Orbiter: the heliospheric explorer
[click here for abstract] Solar Orbiter - ESA M1 Mission - has entered its scientific phase at the end of November 2021, after a cruise phase of more than 18 months (and 2.2 Billion km) and the commissioning of the 10 instruments on board. CEA/IRFU played a key role in this mission, by providing the focal plane detector array of the X-ray telescope, STIX, based on in-house Caliste technology. In the meantime, solar physicists have been busy preparing the pipelines needed to handle the data sent by the instrument, and developing high performance numerical simulations of the Sun.
In this 2-voice seminar, we will relate the first 26 months of activities of the mission, covering both STIX calibration, its first light, the first solar flare detected, as well as the development of associated numerical simulations of the Sun and optimal scientific processing of instrumental data sent as the spacecraft gets closer and closer to the Sun (last perihelion was on 26 March 2022 at 0.32 AU), while in the meantime our star is increasing in intensity and in activity, with solar magnetic cycle 25 now well on its way. Local contact: Pierre-Antoine FRUGIER; organization: Pierre-Antoine FRUGIER |
Tuesday May 3 | Vacations / Vacances Vacances de printemps |
Tuesday May 10 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Lev TITARCHUK (University of Ferrara, Italy)
Comptonization Problem and Its solution in Application to the Spectra of the Neutron Star and Black Hole Sources
[click here for abstract] In 2017 the work on the Comptonization (Sunyaev-Titarchuk) seen in the X-ray spectra of astrophysical sources was a candidate for the Nobel Prize in Physics. In this talk I provide all the details of the exciting prehistory of this topic and precise details of this discovery. The solution of this problem and its subsequent development and application to the spectra of accreting neutron star (NS) and black hole (BH) binaries reveals a lot of information on these objects. In particular, now we can unambiguously distinguish between a NS and a BH (Galactic or extragalactic) using correlations of their spectral indices vs mass accretion rate (or QPO frequency). I further demonstrate how we can determine a BH mass using this correlation. Local contact: Philippe LAURENT; organization: Frédéric GALLIANO |
Tuesday May 17 10:00 | Recent hiree seminar / séminaire arrivant récent Benjamin MAGNELLI (DAp)
A decade of the main-sequence of star-forming galaxies: New insights and perspectives on massive galaxy formation
[click here for abstract] The observed tight correlation between the star formation rate (SFR) and the stellar mass of star-forming galaxies (SFGs) is now well constrained over the last 10 Gyr of look-back time. This so-called main sequence (MS), whose normalization declines from z~3 to 0, is commonly interpreted as evidence that SFGs are evolving primarily through a steady and long star-forming mode, likely sustained by the cold gas accretion along the cosmic web. Over the last decade, a plethora of studies have investigated within this framework the physical properties of SFGs along and across the MS, establishing key scaling relations between, e.g., the stellar mass, gas content, and/or morphology of SFGs in the SFR-stellar mass plane. In this talk I will review past and recent observational evidences of this new MS paradigm and how it has shaped our understanding of the evolution of massive galaxies. Then, I will present the limitations of this simple paradigm, and in particular how it fails to explain the more diverse than anticipated population of MS galaxies (e.g., starburst hidden within the MS), the importance of secondary parameters (e.g., environment) and the transition of SFGs to quiescence. I will conclude by presenting future observational opportunities that can be used to investigate this hidden complexity within the main sequence and to further unveil the physics involved in the evolution of massive galaxies over cosmic time. Local contact: Benjamin MAGNELLI; organization: Carlos GOMEZ GUIJARRO |
Tuesday May 31 10:00 | Cancelled / séminaire annulé Elisa COSTANTINI (SRON, Netherlands)
[TBA]
Local contact: Anne DECOURCHELLE; organization: Frédéric GALLIANO |
Tuesday June 14 10:00 | Diego GÖTZ et Aline MEURIS (DAp)
The MXT telescope on board SVOM: a new tool for time-domain and multi-messenger astrophysics
[click here for abstract] The Sino-French SVOM (Space based astronomical Variable Object Monitor) mission is ready for launch in 2023. This mission is dedicated to the study of Gamma-Ray Bursts and other transient and variable sources of the high-energy sky. On board SVOM there will be four instruments, ECLAIRs and GRM, with large field of views, operating in the hard X- and gamma-ray domain, and two narrow field instruments: the Visible Telescope (VT) and the Microchannel X-ray Telescope (MXT). The MXT is a novel kind of compact and light instrument based of the « Lobster Eye » optical concept, coupled to a low noise state-of-the art X-ray camera, the latter being designed and manufactured at CEA Irfu. For a total mass of 42 kg and a total power of 60 W, this instrument is composed of an optics system, a telescope tube in carbon fiber, a radiator, a camera and a data processing unit. The 9 kg camera consists of a focal plane assembly with a detector assembly and thermoelectrical coolers, a front-end electronics assembly, a calibration wheel assembly and a support structure assembly. We will first review the SVOM scientific objectifs and how MXT will contribute to reach them. Then we will present the MXT design in more detail, focussing on the CEA contribution, and finally we will present the results of the calibration campaign performed in 2021 before the delivery of the telescope to Cnes. Local contact: Pierre-Antoine FRUGIER; organization: Pierre-Antoine FRUGIER |
Tuesday June 21 10:00 | Recent hiree seminar / séminaire arrivant récent Sandrine CODIS (DAp)
Modeling the birth and growth of the cosmic web
[click here for abstract] Starting from the largest scales, I will first describe how the cosmic web is woven across cosmic time into a gigantic bubble-like tapestry made of nodes, filaments, walls and voids. A particular emphasize will be put on the geometry and connectivity of this cosmic foam. Recent theoretical works aiming to precisely model the Universe on those mildly non-linear scales will be presented. In particular, I will identify a regime where large-deviation theory can be successfully implemented to predict the so-called count-in-cells statistics and describe promising cosmological applications for future galaxy surveys. The second part of the talk will focus on the birth and evolution of haloes and galaxies within these large cosmic highways. The highly anisotropic galactic environment set by the cosmic web will be shown to play a significant role in shaping them, an effect inducing large-scale galaxy alignments that are difficult to model but represent an important contamination for weak lensing experiments. Local contact: Sandrine CODIS; organization: Carlos GOMEZ GUIJARRO |
SUMMER BREAK | |
Tuesday September 6 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Nicolas SCEPI (CU Boulder)
Formation, Evolution and Radiation of Magnetized Accretion Disks around Black Holes
[click here for abstract] The impact of magnetic fields on the evolution and on the observational signatures of accretion disks is very uncertain. This uncertainty is mainly due to a lack of observational constraints on the magnetic field geometry or strength in accretion disks. However, even from a theoretical point of view our understanding of magnetized disks remains relatively poor. Indeed, analytic models of magnetized disks often need inputs from numerical simulations and numerical simulations of magnetized disks are difficult to perform and/or interpret. Because of this lack of magnetized disk models, standard disk models often reduce the magnetic field to a source of turbulence; turbulence through which the accretion can happen. While this simplification may hold for weakly magnetized disks, a large number of numerical simulations have shown that the role of a strong magnetic field goes far beyond producing turbulence. In particular, a strong magnetic field can produce powerful outflows, induce accretion through vertically elevated layers or non-axisymmetric structures, modify the time scales of accretion, enhance dissipation of gravitational energy in the disk and accelerate particles to very high energies. All of these effects dramatically affect the evolution and observational signature of accretion disks and open up new and exciting avenues to resolve outstanding problems of the standard accretion disk theory. In this talk, I will present an overview of my recent results on how strongly magnetized disks form, evolve and radiate. I will show in particular how strongly magnetized disks could explain events of very strong variability in AGNs, the flaring behavior of the Galactic center and the hardest emission in X-ray binaries. Local contact: Jérôme RODRIGUEZ; organization: Matteo BUGLI |
Tuesday September 13 10:00 | Special seminar / séminaire exceptionnel Elisabeth KOHLER (CNRS)
Agir pour l’égalité professionnelle entre les femmes et les hommes
[click here for abstract] De la scolarité aux postes à responsabilité de nombreux stéréotypes persistent qui souvent entravent la carrière scientifique des femmes. L’objectif de ce séminaire est d’identifier ces biais et de présenter des exemples de mesures concrètes pour y remédier et mettre en œuvre des politiques d’égalité professionnelle entre les femmes et les hommes. Différents sujets seront abordés, tels que les critères d’évaluation, les actions de communication, le congé maternité et la parentalité, la lutte et la prévention contre les violences sexistes et sexuelles. Local contact: Anaëlle MAURY; organization: Frédéric GALLIANO |
Tuesday September 27 10:00 | [TBA] |
Tuesday October 4 | Special event / Événement spécial |
Tuesday October 11 10:00 | Special radio seminar / séminaire spécial radio Françoise COMBES (LERMA)
Overview of Cosmology with SKA, the Square Kilometer Array
[click here for abstract] SKA is a new technology radio-telescope array, about two orders of magnitude more sensitive and rapid in sky surveys than present instruments. It will be able to detect and measure the redshifts of billions of galaxies at the redshifts up to z=2, to probe through baryonic acoustic oscillations the nature of dark energy; it will probe the cosmic dawn of the universe, just afer recombination, and during the epoch of reionisation (z=6-15); it will be the unique instrument to map the atomic gas in high redshift galaxies, and determine the amount and distribution of dark matter in the early universe. With SKA-VLBI, it will unveil the accretion and feedback processes near super-massive black holes, and results from precursors will be shown. We will discuss these exciting perspectives, which will concretize at the end of the decade. Local contact: Marc-Antoine MIVILLE-DESCHÊNES; organization: Marc-Antoine MIVILLE-DESCHÊNES |
Thursday October 13 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Jordan PHILIDET (Max Planck Institute for Solar System Research, Göttingen)
Impact of turbulent convection on stellar oscillations
[click here for abstract] The study of the global oscillations of stars, which is at the heart of asteroseismology, has enabled us to make significant progress in our
understanding of stellar physics. In Sun-like stars, these oscillations are affected by the turbulent motions entailed by the convective instability in the envelope. In addition to modifying the resonant frequencies of the modes, turbulent convection is also responsible for their excitation, as well as part of their damping. As such, solar-like oscillations gives us access to crucial information about stellar convection, which constitutes one of the main obstacles towards better stellar modelling. However, in order to exploit the wealth of asteroseismic data at our disposal to better constrain the properties of stellar convection, it is necessary to theoretically model the relation between these properties and the asteroseismic observables (namely the amplitude of the modes, their lifetime, and the amount by which convection shifts their frequencies, referred to as surface effects).
In this talk, I will first focus on solar-like acoustic modes. Traditional approaches to study the effect of convection thereon are either based on parametric empirical formulations, or else on 3D simulations. These approaches show unavoidable limitations, among which the impossibility to realistically describe the full turbulent cascade, and especially the turbulent dissipation of kinetic energy. Here, I will present a new alternative theoretical framework designed to circumvent these limitations, based on Lagrangian stochastic models. I will demonstrate how, under reasonable assumptions, this sort of formalism can lead to simultaneous theoretical estimates for the amplitude, lifetime and surface effect of the acoustic modes, directly as a function of the turbulent fluctuations caused by convection, thus allowing to constrain turbulent convection models through the direct comparison of these estimates with observed mode properties. The second part of this talk will focus on another kind of oscillations, namely the inertial modes recently observed on the surface of the Sun. These modes propagate under the action of rotation, through the Coriolis acceleration, and, for the most part, are predicted to be stable, meaning that they are likely also excited by turbulent convection, just like acoustic modes. In order to test that hypothesis, I will present a theoretical formalism where the turbulent velocity fluctuations provide the mechanical work necessary to excite the modes, which are described by means of a 2D linear wave equation, under the β-plane approximation. Based on the general agreement between the predicted and observed inertial mode amplitudes, I will show that the (linearly stable) solar inertial modes are indeed excited by turbulent convection. This formalism also shows that the power in high azimuthal order spectra is not easily separable into individual modes, thus complicating the interpretation of the observations. Local contact: Stéphane MATHIS; organization: Frédéric GALLIANO |
Tuesday October 18 | Special event / Événement spécial |
Tuesday October 25 | Vacations / Vacances Vacances de la Toussaint |
Tuesday November 8 10:00 | Philippe Laurent, Aymeric Sauvageon, Jérôme Rodriguez (DAp)
INTEGRAL : 20 ans dans l'espace pour une aventure de plus de 35 ans
[click here for abstract] Le laboratoire INTErnational d'Astrophysique des Rayons Gamma (INTEGRAL) a été lancé le 17 octobre 2002 de Baikonour (Kasakstan). Depuis lors il est resté sur son orbite elliptique de haute excentricité (environ 3 jours) effectuant 2568 révolutions (au 8 novembre 2022) autour de la Terre pour environ 530 Ms (méga secondes) d'observations scientifiques. Cette mission de taille moyenne transporte deux instruments principaux opérant dans le domaine spectral des rayons X durs et des rayons gamma mous (20keV-10 MeV), dont l'optique est basée sur le concept de masques codés : l'un est dédié à l'analyse spectrale fine avec des capacités d'imagerie modérées (SPI), l'autre est dédié à l'imagerie fine (ou presque) avec des capacités spectrales modérées (IBIS).
Ces 20 ans dans l'espace sont le résultat d'au moins 15 ans de développement du projet avant qu'INTEGRAL puisse dévoiler le mystère du ciel à haute énergie. Le Dap a été profondément impliqué dans cette aventure de longue haleine, depuis le tout début du développement du concept de la mission (grande implication dans les deux instruments, ISGRI et SPI, participation au centre de données, développement de l'analyse s/w, suivi de la caméra) jusqu'à l'analyse actuelle des données en temps réel et des archives, avec un grand nombre d'articles publiés dans tous les domaines permis par les capacités instrumentales et même au-delà. Nous allons, dans ce séminaire, résumer ces plus de 35 ans en présentant divers aspects du projet/de la mission, en nous concentrant particulièrement sur ceux où l'implication du Dap a été cruciale. Nous commencerons par une vue d'ensemble de l'histoire de la mission, des principales caractéristiques instrumentales et des objectifs scientifiques au lancement, puis nous nous concentrerons sur la caméra ISGRI, la couche de détection 20-250 keV du télescope IBIS, qui est suivie au Dap tous les jours. ISGRI a été développée à l'IRFU et a obtenu la plupart des résultats d'INTEGRAL. Nous conclurons par un aperçu rapide et évidemment biaisé de quelques résultats scientifiques obtenus au cours de ces 20 années. Le séminaire sera présenté en Français avec des diapositives en Anglais par Philippe Laurent, Aymeric Sauvageon et Jérôme Rodriguez, bien humblement au nom d'un grand nombre de collègues anciens et actuels. ―――――――――――――――――――――――――――――――――――――――――― ENGLISH VERSION INTEGRAL : 20 years in space and for a 35+ years adventure The INTErnational Gamma-Ray Astrophysics Laboratory (INTEGRAL) has been launch on October 17th, 2002 from Baikonour (Kasakstan). Since then it has remained on its high-eccentricity elliptical orbit (about 3 days) performing 2568 revolutions (as of Nov. 8th, 2022) around the Earth for around 530 megaseconds of scientific observations. This medium sized mission caries two main instruments operating in the spectral domain of hard X-rays/Soft Gamma-rays (20keV-10 MeV), whose optics is based on the concept of coded masks: one is dedicated to fine spectral analysis with moderate imaging capabilities (SPI) the other is dedicated to fine(-ish) imaging with moderate spectral capabilities (IBIS). These 20 years in space are the results of at least 15 years of project development before INTEGRAL could unveil the mystery of the high-energy sky. The DAp has been deeply involved in this long-term adventure from the very beginning of the mission concept development (large involvement in both instruments, ISGRI and SPI, participation to the data centre, development of the s/w analysis, monitoring of the camera) to the current analysis of real time and archival data, with a large number of published papers in all fields allowed by the instrumental capabilities and even beyond. We will, in this seminary, summarised these 35 years+ by presenting various aspects of the project/mission, focusing especially on those where the involvement of the Dap has been crucial. This will start with an overall overview of the mission history, the main instrumental characteristics and scientific goals at launch, followed by a focus on the ISGRI camera, the 20-250 keV detector layer of the IBIS telescope, which is followed-up at DAp every days. ISGRI has been developed at IRFU and obtained most of the INTEGRAL results. We will conclude with a quick and obviously biased overview of some scientific results obtained over these 20 years. The talks will be given by Philippe Laurent, Aymeric Sauvageon, and Jérôme Rodriguez humbly on behalf of many, many former and current colleagues and presented in French with slides in English. Local contact: Pierre-Antoine FRUGIER; organization: Pierre-Antoine FRUGIER |
Tuesday November 15 10:00 | Large project seminar / séminaire grand projet Anaëlle MAURY (LFEMI)
Magnetic fields from star-forming cores to protostellar disks: a review of major contributions from the MagneticYSOs project
[click here for abstract] Wherever we have the means of observing them, magnetic fields are detected across the full spectrum of astrophysical environments, from our own Earth, to stars, and cosmological structures. Magnetic fields are also present at all scales and evolutionary stages of star-forming structures. They have long been suspected to play a key role in shaping the typical outcome of the star formation process, such as stellar mass, spin, and multiplicity, or even the fate of stars towards their ultimate stages.
In this talk, I will provide a global outlook on the progresses made in the recent years to characterize the role of magnetic fields during the embedded phases of the star formation process. Thanks to the development of observational capabilities and the parallel progress in numerical models capturing most of the important physics at work during star formation, the MagneticYSOs team successfully confronted detailed predictions of magnetized models to observational properties of the youngest protostars. I will present the physical processes and observational methods allowing to trace the magnetic field in embedded protostars, and review the main steps, success and limitations in comparing real observations to synthetic observations from the non-ideal MHD models. I will show how our work has shed light on the physical conditions required to ensure an efficient magnetic field coupling, and present unexpected results regarding the two main agents responsible for the coupling in star-forming cores: dust grains and ionized gas. Following this Ariane thread, I will argue our observational and theoretical findings support a novel scenario where the angular momentum problem for star formation may be actually “solved” not by the formation of large protoplanetary disks but by the combination of 1) lack of organized rotation motions at large envelope radii, 2) the inefficient angular momentum transport due to magnetic braking in the inner envelope (and angular momentum removed through rotating outflows generated by the presence of the magnetic field), and 3) a local origin of the angular momentum incorporated in the star–disk system. Reference review Local contact: Anaëlle MAURY; organization: Frédéric GALLIANO |
Friday November 18 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Camille DIEZ (University of Tübingen)
Using Vela X-1 to understand accretion and wind structure in neutron star High-Mass X-ray Binaries (HMXBs)
[click here for abstract] The spectral and timing behaviour of HMXBs offers a unique opportunity for the investigation of accretion onto compact objects and of wind structure in massive stars. The bright and persistent neutron star HMXB Vela X-1 is one of the key systems for such studies with both current and future instruments. It has a complex clumpy stellar wind, prominent cyclotron resonant scattering features (CRSFs) and strong flares. Understanding the variability of the systems on both short time scales of a few hundreds seconds and along its 9d orbit with current instruments enables us to make predictions for future observations with XRISM and Athena and to devise the best observational strategy for Vela X-1. Here, we analyse two new observations taken with NuSTAR and XMM-Newton at orbital phases ~0.5 and ~0.75 and follow the evolution of spectral parameters down to the pulse period (~300s) time-scale. The flux-dependency we observe in the spectral shape implies a change in the properties of the Comptonising plasma and the observed drop of the CRSF energy following a strong flare may indicate a change in the accretion geometry. The strong variability of absorption is due to the presence of a large-scale wind structure, such as accretion- and photoionisation wakes, combined with the variable line of sight as the neutron star moves along the orbit. In particular, we, for the first time, are able to trace the onset of the wakes with high time resolution and compare to predictions from simulations. Local contact: Jérôme RODRIGUEZ; organization: Frédéric GALLIANO |
Tuesday November 22 10:00 | Recent hiree seminar / séminaire arrivant récent Antonio GARCIA MUÑOZ (DAp)
Exoplanet atmospheres: An anticipated revolution
[click here for abstract] The launch of the JWST less than a year ago is expected to set a turning point in exoplanet science, which is progressively transitioning from detection and population statistics to in-detail characterization of the exoplanets’ atmospheres. In this talk, I will present an admittedly biased
perspective of what this may represent for our understanding of exoplanets, and how ongoing theoretical work and future telescopes may build upon JWST’s legacy. Local contact: Antonio GARCIA MUÑOZ; organization: Frédéric GALLIANO |
Friday November 25 14:30 | Special seminar / séminaire exceptionnel Leïla GODINAUD, Anne DECOURCHELLE, Fabio ACERO (DAp)
De Nova Stella : Séminaire d'anniversaire des 450 ans de la supernova de Tycho
[click here for abstract] En novembre 1572, l'observation de l'apparition d'une "nouvelle étoile" dans le ciel et les observations détaillées réalisées par Tycho Brahe ont transformé la façon dont nous voyons et comprenons notre Univers. Pour marquer l'événement, nous proposons un séminaire en trois parties allant de l'observation historique de l'événement jusqu'aux connaissances actuelles sur la supernova SN1572 et son vestige.
La conférence sera suivie d'un café gourmand dans le hall de la salle Galilée. ―――――――――――――――――――――――――――――――――――――――――― ENGLISH De Nova Stella: 450th anniversary seminar for Tycho's supernova In November 1572, the observation of the apparition of a "new star" in the sky and the detailed observations made by Tycho Brahe transformed the way we see and understand our Universe. To mark the event we propose a three-part seminar ranging from the historical observation of the event to the current knowledge about the supernova SN1572 and its remnant. The conference will be followed by a gourmet coffee in the hall of the Galilee room. Local contact: Anne DECOURCHELLE; organization: Frédéric GALLIANO |
Tuesday November 29 10:00 | Elisa COSTANTINI (SRON, Netherlands)
The cold and dusty medium in our Galaxy as seen in the X-rays
[click here for abstract] X-rays have unique advantages in studying absorption and scattering from interstellar dust. For example, sharp and deep absorption features of Mg, Si, O and Fe, which are the building blocks of silicates, fall in the X-ray band. Present X-ray observatories already delivered to us interesting results, challenging the common paradigm on interstellar dust chemical and physical characteristics. Future instruments will open up an unexplored window, revealing the most dense environments of our Galaxy.
In this talk I will illustrate the state-of-art of our understanding of dust as seen in the X-rays, and future prospects, using for example, the upcoming XRISM satellite. Local contact: Anne DECOURCHELLE; organization: Frédéric GALLIANO |
Tuesday December 6 10:00 | David ALONSO (Oxford Department of Physics)
Modeling the birth and growth of the cosmic web
[click here for abstract] In the last 10-20 years we have been able to observe vast swathes of the Universe at different wavelengths, allowing us to build high-sensitivity maps of different projected cosmic properties. The statistical correlation between these properties and the density inhomogeneities that underlie the cosmic large-scale structures can then be used to reconstruct the spatial distribution of fundamental cosmological and astrophysical quantities, as well as their evolution in time. In this talk, I will describe a number of methods used to carry out this kind of tomographic reconstruction, present measurements of fundamental properties (structure growth, gas pressure, star formation rate density) resulting from their application to existing data, and discuss the potential of near-future "Stage-IV" experiments to improve on and benefit from these methods, in their quest to improve our understanding of fundamental physics. Local contact: Denise LANZIERI; organization: Denise LANZIERI |
Tuesday December 13 10:00 | Recent hiree seminar / séminaire arrivant récent Réza ANSARI (DAp)
Cosmology with 21cm Intensity Mapping
[click here for abstract] Intensity Mapping (IM) has been proposed about 15 years ago as an efficient technique to perform cosmological surveys. The 21cm hyperfine transition of neutral hydrogen can indeed be used to map the 3D distribution of matter in the universe, over a wide range of redshifts, from z=0 to z=3 or even z=6, bringing complementary information to the optical surveys.
Since then, few dedicated instruments have been built (CHIME, Tianlai, BINGO) to explore the feasibility of the method; Other more ambitious instruments, such as HIRAX, CHORD or BINGO will be commissioned in the coming years. Intensity mapping surveys are also envisaged for SKA, in addition to the classical HI source surveys. After presenting the principle of 21 intensity mapping, I will briefly discuss its cosmological promises, as well as some of the associated instrumental and scientific challenges. I will then present some of the results of ongoing observations, focusing on Tianlai, and on PAON4. Tianlai is an international project that operates two pathfinder instruments, a cylinder array and a parabolic array, built in Xinjiang, in western China. PAON4 is a small test interferometer, located in Nançay, used to explore some of the technical aspects of compact radio arrays, operating in transit mode. Local contact: Réza ANSARI; organization: Frédéric GALLIANO |
2021 | |
Tuesday January 12 10:00 | [TBA] |
Tuesday January 26 10:00 | [TBA] |
Tuesday February 9 10:00 Salle Virtual seminar | Michelle LOCHNER (AIMS, South Africa)
Anomaly Detection in Astronomical Data using Machine Learning
[click here for abstract] The next generation of telescopes such as the SKA and the Vera C. Rubin Observatory will produce enormous data sets, far too large for traditional analysis techniques. Machine learning has proven invaluable in handling large data volumes and automating many tasks traditionally done by human scientists. In this talk, I will discuss how machine learning for anomaly detection can help automate the process of locating unusual astronomical objects in large datasets thus enabling new cosmic discoveries. Local contact: Virginia AJANI; organization: Virginia AJANI |
Tuesday February 23 | Vacations / Vacances Vacances d'hiver |
Tuesday March 9 10:00 | [TBA] |
Tuesday March 23 10:00 | [TBA] |
Tuesday April 6 10:00 | [TBA] |
Tuesday April 20 | Vacations / Vacances Vacances de printemps |
Tuesday April 27 10:00 | Frédéric BOURNAUD (Departement d’Astrophysique, IRFU, CEA-Saclay et Université Paris-Saclay)
Cosmological simulations of galaxy formation: toward a robust accounting of galaxy populations and star formation across the Universe?
[click here for abstract] Cosmological simulations of galaxy formation are reaching a high level of accuracy and can finely reproduce some of the main properties of galaxy populations: stellar masses, angular momentum, colors, etc. However, most galaxy formation simulations still fail to account for the detailed structure of galaxies and their global star formation history. Using high-resolution, idealized simulations of galactic dynamics and star formation, I will show that these disagreements are not cosmetic details but point toward a fundamental tension between observations and galaxy formation models. Historically, galaxy formation models predicted galaxies with unrealistically large stellar masses: in modern cosmological simulations, this issue is generally solved though energetic feedback from young stars and supermassive black holes. I will nevertheless show that feedback, as implemented in such simulations, is generally excessive, leading to the early and unrealistic exhaustion of interstellar gas reservoirs. Comparisons to idealized simulations and observations of galactic winds support the conclusion that energetic stellar and black hole feedback cannot be entirely responsible for the regulation of star formation and galaxy growth. Other physical processes likely emerge from sub-galactic scales in the interstellar medium, such as subtle coupling between galactic dynamics and star formation through instabilities and turbulence. Nevertheless, some cosmological simulations can now successfully describe the re-distribution of baryons from galaxies to the intergalactic medium, and I will show that these simulations are a crucial tool not just for galaxy formation but also for modern cosmological surveys. I will finally review how simulations of galaxy formation, evolution and star formation could gain strength in the years to come, in relation with the arrival of exascale supercomputers. Local contact: Carlos GOMEZ-GUIJARRO; organization: Carlos GOMEZ-GUIJARRO |
Tuesday May 4 10:00 | [TBA] |
Tuesday May 18 10:00 | [TBA] |
Tuesday June 1 10:00 | [TBA] |
Tuesday June 15 | Special event / Événement spécial |
Tuesday June 29 10:30 | Jérôme AMIAUX et Pierre-Olivier LAGAGE (Array)
La Mission ARIEL
[click here for abstract] Ariel est la mission M4 du programme ‘Cosmic Vision’ de l’ESA. C’est une mission entièrement dédiée à l’étude de l’atmosphère des exoplanètes ; un millier d’exoplanètes vont être scrutées. La France apporte une contribution majeure à cette mission en ayant la charge du développement de l’instrument principal d’Ariel : le spectromètre InfraRouge AIRS 2-8 microns. Ce développement se fait sous maitrise d’ouvrage du CNES et maitrise d’œuvre du DAp-AIM ; les autres laboratoires participants sont l’IAS, le LESIA et l’IAP. Dans ce séminaire nous présenterons la mission, ses enjeux scientifique et techniques avec un zoom sur la contribution française. Local contact: Pierre-Antoine FRUGIER; organization: Pierre-Antoine FRUGIER |
Tuesday November 9 10:00 | [TBA] |
Tuesday November 23 10:00 | Special seminar / séminaire exceptionnel Talk in French; slides in English. Michel TOULMONDE (SYRTE, Observatoire de Paris)
Émilie du Châtelet et les Principia de Newton
[click here for abstract] Selon Newton, la cause des mouvements des planètes et des comètes est la gravitation universelle qui crée les forces nécessaires pour que ces astres se déplacent sur des orbites elliptiques autour du Soleil. Il publie ce travail en 1687 dans sa grande œuvre les Philosophiæ naturalis principia mathematica, communément appelée les Principia.
Très admirative de ces idées nouvelles, Émilie Du Châtelet traduit en français le texte latin des Principia dans le but de les diffuser. Son action n'est pas solitaire : Maupertuis, Voltaire et Clairaut notamment vont la soutenir dans sa lourde tâche, car plusieurs savants français n’acceptent pas l’idée d’action à distance que serait la gravitation. Après le décès d'Émilie en 1749, Clairaut devient l'éditeur du manuscrit des Principes mathématiques de la Philosophie naturelle, mais l’ouvrage ne sera publié que dix ans plus tard, en 1759. À l’occasion de la parution d’une nouvelle édition critique de ce livre, on reverra les apports fondamentaux de Newton, puis on regardera le manuscrit d’Émilie Du Châtelet et on verra le rôle de Clairaut dans la parution tardive des Principes et du Commentaire écrits par « l’immortelle Émilie ». Local contact: Koryo OKUMURA; organization: Frédéric GALLIANO |
Tuesday December 7 10:00 | [TBA] |
Tuesday December 21 | Vacations / Vacances Vacances de Noël |
2020 | |
Tuesday January 14 10:00 | J. Biteau (IPNO, Université Paris-Sud, Univ. Paris/Saclay, CNRS/IN2P3)
Astroparticles from the extragalactic universe
[click here for abstract] Besides the classic heralds of astronomy, from radio waves to X-rays, the past two decades have seen the emergence of four fantastic messengers: astroparticles. Gravitational waves, GeV-TeV gamma rays, PeV neutrinos, and cosmic rays at EeV energies and above are all now, since 2015, informants on the conditions prevailing in the most extreme accelerators that our universe houses. In this talk, I will illustrate the first steps of multi-messenger astronomy with gamma-ray and cosmic-ray signals that have traveled to our ground-based detectors from cosmic scales, ranging from the innards of our super-cluster, Laniakea, to a time when the universe was only a fifth of its current age, beyond z ~ 2. Astroparticles from the most extreme extragalactic emitters not only enable the probe of particle acceleration at energies beyond the reach of human-made facilities, but can also be exploited as tracers of the electromagnetic content of the universe. Magnetic and photon fields populating the largest voids in the cosmos are starting to reveal their mysteries, setting the grounds for the newborn field of gamma-ray cosmology and long-awaited cosmic-ray astronomy. Major astroparticle observatories are under upgrade or construction and they hold a formidable scientific potential for current and next-generation researchers. Local contact: J. Rodriguez, T. Stolarczyk; organization: J. Rodriguez, T. Stolarczyk |
Tuesday January 28 10:00 | P. Moesta (University of Amsterdam)
Jet-driven supernovae in the multimessenger era
[click here for abstract] Jet-driven core-collapse supernovae belong to the most energetic transients in the universe and are key targets for time-domain astronomy surveys. I will discuss the unique challenges in both input physics and computational modeling for these systems involving all four fundamental forces and highlight recent breakthroughs in full 3D simulations. I will pay particular attention to how these simulations can be used to reveal the engines driving these events and conclude by discussing what remains to be done in order to maximize what we can learn from current and future time-domain transient surveys. Local contact: J. Guilet; organization: M. Bugli |
Tuesday February 11 | Vacations / Vacances Vacances d'hiver |
Tuesday February 25 10:00 | J. Forbrich (University of Hertfordshire)
In Dust we Trust, from Orion to Andromeda - Molecular clouds from our Galactic backyard to Andromeda's neighbourhoods
[click here for abstract] Studies of 'nearby' molecular clouds - within a distance of a few 100 pc and with the Orion Molecular Cloud as the most prominent example - have revealed the physics of star formation in exquisite detail - ranging from density profiles of clouds from dust extinction mapping to accurate star formation rates from counting young stellar objects. Larger samples of clouds are needed to place these local results in a more complete context. The arguably best way to obtain a large reference sample of clouds would be to observe resolved individual molecular clouds in the Andromeda Galaxy (M31), as the most nearby large spiral galaxy with close to Galactic metallicity - importantly using dust rather than gas as the primary tracer, just as for the local clouds, enabling a direct comparison. Fortunately, with wideband continuum radio interferometers, this is now becoming possible. I will present first results of a large program targeting M31 with the Submillimeter Array (SMA). Using the SMA's wideband capabilities, we have not only demonstrated that direct detection of resolved continuum emission from individual clouds is now possible on scales of 10-15 pc in M31, but we can even concurrently measure CO within the same observational setup. This ensures identical calibration and spatial filtering of dust and gas measurements, providing unique constraints on cloud identification and the CO 'X' factor for a large number of molecular clouds. Given the meaningful overlap in physical resolution with measurements of local clouds, this experiment will truly enable us to compare the local molecular clouds with a significant fraction of the cloud population of the Andromeda Galaxy. The main goals of the project include a cloud-scale assessment of star formation laws as well as of cloud properties as described by Larson's relations. Local contact: M. Galametz; organization: M. Galametz |
Tuesday March 10 | Special event / Événement spécial |
Tuesday March 24 10:00 | Cancelled / séminaire annulé |
Tuesday April 7 | Vacations / Vacances Vacances de printemps |
Tuesday April 21 10:00 | Cancelled / séminaire annulé |
Tuesday May 5 10:00 | Cancelled / séminaire annulé |
Tuesday May 19 10:00 | Cancelled / séminaire annulé Ariel SÁNCHEZ (MPE)
[TBA]
Local contact: Virginia AJANI; organization: Virginia AJANI |
Tuesday June 2 | Special event / Événement spécial |
Tuesday June 16 10:00 | Cancelled / séminaire annulé Michel TOULMONDE (SYRTE, Observatoire de Paris)
Émilie du Châtelet et les Principia de Newton
[click here for abstract] ... Local contact: Koryo OKUMURA; organization: Frédéric GALLIANO |
Tuesday June 30 10:00 | Cancelled / séminaire annulé |
SUMMER BREAK | |
Tuesday September 29 10:00 | Stéphane MATHIS (LDE3)
Understanding the evolution of planetary systems: angular momentum exchanges from the core of the host stars to planetary
Local contact: Stéphane MATHIS; organization: Matteo BUGLI |
Tuesday October 6 10:00 | Michael LE BARS (IRPHE)
Dynamics at the convective/radiative zones interface: an experimental approach
Local contact: Thierry FOGLIZZO; organization: Matteo BUGLI |
Tuesday October 20 10:00 | François LANUSSE (LCS)
Merging deep learning with physical models for the analysis of modern cosmological surveys
Local contact: François LANUSSE; organization: Virginia AJANI |
Tuesday November 3 10:00 | Cancelled / séminaire annulé |
Tuesday November 17 10:00 | Cancelled / séminaire annulé |
Tuesday December 1 10:00 | Cancelled / séminaire annulé |
Tuesday December 15 10:00 | Cancelled / séminaire annulé |
2019 | |
Tuesday January 8 10:00 | Special seminar / séminaire exceptionnel A. Vigan (LAM)
Direct Imaging of Exoplanets with VLT/SPHERE: Past, Present and Future
[click here for abstract] SPHERE is the new generation exoplanet imagers installed at the Very Large Telescope. Since 2015, we have started the large-scale SHINE survey to look for giant exoplanets around a sample of 400 to 600 young, nearby stars (younger than 300 Myr, closer than 150 pc). The main goal of SHINE is to constrain for the first time the population of giant exoplanets in the 5-100 AU range, where previous direct imaging surveys and other detection methods are not sensitive. After describing the SPHERE instrument and the astrophysical context, I will present the current status of SHINE, some of its recent discoveries and the first statistical constraints drawn after 4 years from a sub-sample of 200 observed targets. Finally, I will conclude with instrumental considerations by presenting some evolutions foreseen for the instrument over the next few years. Local contact: P.-O. Lagage, P. Tremblin; organization: M. Bugli |
Tuesday January 15 10:00 | D. Allard (APC)
Multi-messenger constraints on the origin of ultra-high energy cosmic-rays
[click here for abstract] After a short introduction on ultra-high-energy cosmic-ray (UHECR) physics, I will discuss the implications of the recent Fermi-LAT
data regarding the extragalactic gamma-ray background, as well as IceCube very-high energy neutrino data, for the origin of
UHECRs.I will show how calculations of the diffuse flux of cosmogenic γ-rays and neutrinos, produced during the propagation of UHECRs in the
extragalactic medium, can provide constraints on the possible cosmological evolutions of UHECR sources. I will present in more
details the mixed-composition scenario considered in several papers by Globus et al. (which is in agreement with most UHECR data)
and show that this model is compatible with both the Fermi-LAT measurements and the current IceCube limits.
I will finally discuss the possibility for future experiments to detect cosmogenic neutrinos and further constrain UHECR models,
including possible subdominant UHECR proton sources. Local contact: J. Ballet; organization: V. Lebouteiller |
Tuesday January 22 10:00 | Special seminar / séminaire exceptionnel M. Giavalisco (Department of Astronomy - UMass Astronomy)
The Evolution of Galaxies: Quenching and Structural Transformations
[click here for abstract] Both in the present-day Universe and earlier on, approximately z~3, we have documented profound structural differences between star-forming and quiescent galaxies. The former host their star formation in rotating disks (thinner and colder today, apparently thicker and hotter at high redshifts), the latter are predominantly dynamically hot systems and have spheroidal morphology, At high redshift (z>1) and up to when quiescent systems can be reliably identified (z~3-4), dynamical information becomes more uncertain, at least in passive systems, but this dichotomy seems to persist at least morphologically. Therecent discovery that disks at high redshift (2 Local contact: E. Daddi; organization: M. Galametz |
Tuesday January 29 10:00 | J. Lasue (IRAP)
Rosetta: 2 years of studying comet 67P/Churyumov-Gerasimenko
[click here for abstract] Comets are icy bodies remnants of the earliest moments of the solar
system formation and that are now studied in details by space missions.
The most recent spacecraft, Rosetta, has ended its studies in September
2016 after having landed Philae for the first time on the surface of a
cometary nucleus and followed 67P on its orbit for more than two Earth
years. The on-board scientific instruments have demonstrated the
sporadic behavior of the cometary activity as a function of its orbital
properties. Cameras have unveiled an irregular surface prone to erosion
and deposition of dust, with few spots of ice detected on its surface.
Dust particles detectors have shown that two types of solid particles
are ejected by the nucleus, one being dense and compact grains and the
other being very fluffy irregular dust particles. No specific structures
inside the cometary nucleus were detected by instruments sounding inside
the nucleus, and the very low density of the cometary material (0.5
g.cm-3) remains difficult to explain. Gaseous particles ejected by the
comet contain a high fraction of O2 and complex carbonaceous molecules
like glycine, an amino acid that was first detected in situ by Rosetta.
We will review the results from the whole Rosetta/Philae mission and
describe in details what we have learned about these objects. Local contact: V. Lebouteiller; organization: V. Lebouteiller |
Tuesday February 12 10:00 | F. Pozzi (Università di Bologna)
The Herschel heritage: tension between the Herschel and SCUBA-2 results?
[click here for abstract] Cosmic dust absorbs the optical/UV photons produced by stars and SMBH and re-emits the energy at longer wavelengths in the IR regime. Infrared observations are, therefore, crucial to achieving a complete picture of the star-formation density (SFRD) , and to understanding the properties of dust across cosmic time. Thanks to the latest IR Herschel satellite (2009-2013), a comprehension of the SFRD was estimated up to z~3-4, but recent observations in the sub-mm regime (SCUBA-2) show discrerpancies with previous Herschel results. I will discuss the possible reasons for this discrepancy and show the critical role that the IR SPICA will play in the future . Local contact: E. Daddi; organization: M. Galametz |
Tuesday February 26 | Vacations / Vacances |
Tuesday March 12 10:00 | M. Barthélémy (IPAG)
Nanosats as an opportunity for space weather
[click here for abstract] Space weather is extremely demanding in term of space data for solar,
magnetospheric or ionospheric survey. Small satellites are interesting
in the sense they are easier to build, cheaper and then accessible to
new entities like countries without space history, SMEs and
universities. Due to their lowest costs, they also can be launched in
constellation for better spatial or temporal coverage. As a complex
science dealing with a chain of phenomenon coming from the sun to the
Earth through the magnetosphere, space weather can benefits from the
multiplication of satellites.
After an introduction based on the potentialities and constraints of
cubesats, we will focus on two example, AMICal Sat and ATISE developed
at the CSUG in Grenoble. We will then extend these example to explain
why space weather is a priority application of the cubesats and give a
large overview of the project in development. Local contact: S. Brun; organization: M. Bugli |
Thursday March 21 10:00 | Special seminar / séminaire exceptionnel N. Martin, N. Flagey (Observatoire de Strasbourg, CFHT)
Maunakea Spectroscopic Explorer - the premier 10m class spectroscopic survey observatory for the next decades
[click here for abstract] The Maunakea Spectroscopic Explorer (MSE, formerly Next Generation CFHT) is an advanced project to profoundly transform the current CFHT into a survey telescope with a 10-meter mirror and a dedicated, heavily multiplexed, wide-field spectrograph with a wavelength coverage of 0.4-1.8 micron and multiple spectral resolutions. MSE is borne out as the response to the astronomical community's need for a large aperture, dedicated, spectroscopic survey facility in synergy with imaging surveys (LSST, WFIRST, ...) and giant telescopes (GMT, ELT, TMT). The project is now entering preliminary design phase after successfully completing its conceptual design.
We will present the current architecture of the observatory as well as the expected performance characteristics of the project and describe the science that is driving this unique facility: unveiling the properties of the faint universe, whether they relate to the origin and diversity of stellar systems, Milky Way archaeology at the earliest time, galaxy evolution across cosmos times, or illuminating the dark universe. Finally, we will conclude with an overview of the project's partnership and organization. Local contact: S. Chabanier; organization: V. Lebouteiller |
Tuesday March 26 10:00 | no seminar - AG Irfu |
Tuesday April 9 10:00 | S. Aalto (Chalmers University, Sweden)
Feeding and feedback - molecular gas in AGNs and starbursts
[click here for abstract] Cold gas plays a central role in feeding and regulating star formation
and growth of supermassive black holes (SMBH) in galaxy nuclei.
Particularly powerful activity occurs when interactions of gas-rich
galaxies funnel large amounts of gas and dust into nuclei of luminous
and ultra luminous infrared galaxies (LIRGs/ULIRGs). These dusty objects
are of key importance to galaxy mass assembly over cosmic time.
It is also increasingly clear that feedback from star formation and AGNs
is fundamental to regulating the evolution of galaxies in the nearby
Universe as well as at earlier epochs.
Mechanical feedback occurs in the form of winds, turbulence, supernova
bubbles and superbubbles, AGN jets and backflows. There is mounting
evidence that massive amount of cold molecular gas is being expelled
from galaxy nuclei and starburst regions by the feedback process. With
the advent of ALMA and the NOEMA telescopes we can now study the
structure, physical conditions and chemistry of the cold flows and the
dusty nuclei at unprecedented sensitivity and resolution.
I will focus on recent ALMA and NOEMA studies of AGN and starburst
outflows from dusty galaxies. I will, for example, present recent ALMA
studies with resolutions of 20 milli arcseconds (2 – 7 pc) of the launch
regions of molecular outflows and jets in the nearby LIRGs NGC1377 and
IC860. These outflows are different from each-other where NGC1377 shows
a 150 pc scale radio-quiet molecular jet (that appears to be precessing)
while the IC860 flow is exceedingly compact and dense and appears to be
in a young phase. I will also discuss observational methods that reach
behind the curtain of dust in the most obscured
centers of U/LIRGs , allowing us to undertake new studies of heretofore
hidden, rapid evolutionary phases of galaxy nuclei. Local contact: V. Lebouteiller, M. Galametz; organization: V. Lebouteiller, M. Galametz |
Tuesday April 16 10:00 | Special seminar / séminaire exceptionnel L. Van Waerbeke (University of British Columbia, Canada)
Axion Quark Nuggets: a candidate for baryonic, cold *and strongly interacting* dark matter
[click here for abstract] Let's assume dark matter is a particle. The DM theories
currently tested, either with direct or indirect detection, cover only a
tiny range of the allowed DM parameters space. A new, viable, DM
candidate, the Axion Quark Nugget (AQN), has been proposed by Zhitnitsky
(2003), partly inspired by the quark nuggets (Witten 1984). In the AQN
model, DM particles are very massive (gram mass) and interact very
rarely, but very strongly, with the baryonic sector. They behave as cold
dark matter, and yet are made of regular matter, without contradicting
primordial nucleosynthesis. In this talk, I will review the basic properties of this model and some
of its astrophysical successes obtained so far. I will then discuss
recent work we have done on how this DM interacts with the solar corona
and how the model can be more thoroughly tested in the future. Local contact: J.-C. Cuillandre; organization: M. Bugli |
Tuesday April 23 | Vacations / Vacances |
Tuesday May 7 10:00 | R. Neühauser (Universität Jena, Germany)
Relevance of historical Observations for modern Astrophysics: Solar Activity, Comets, and Galactic Supernovae
[click here for abstract] We will review the relevance of historical observations for current astrophysical problems, in particular for the reconstruction of solar activity in the 17th century Maunder Minimium and the pre-telescopic time - as well as the study of historical supernovae in our Galaxy. Among other observations, we will discuss the strong 14-C variation around AD 775 detected in trees around the world and discuss possible causes like a nearby supernova, a Galactic gamma-ray burst, a solar super-flare, etc. Local contact: M. Galametz; organization: M. Galametz |
Tuesday May 14 10:00 Salle Cassini | Group seminar open to everybody / séminaire de groupe ouvert à tous S. Hernandez (STScI)
Measuring the chemistry of stars to understand the evolution of galaxies
[click here for abstract] Being complex systems containing vast amounts of gas, dust, and stars, galaxies allow us to study the Universe in great detail. It is inside these systems that stars form, and transform the simplest of elements, hydrogen, into heavy elements essential for life as we know it. In the last few years I have worked dissecting galaxies in an effort to obtain clues to their chemical evolution histories. Star clusters, both Globular and Young Massive Clusters (YMCs), are attractive test laboratories for several astrophysical reasons. Given that these objects can be observed and studied in detail at larger distances than individual stars, one can use them as tracers of stellar populations outside of our own Milky Way. Using spectroscopic observations of star clusters covering a broad range of ages (~2 Myr to ~12 Gyr) we probe the chemical enrichment history of the host galaxy. I will discuss recent work exploiting spectroscopic observations acquired with both the ESO Very Large Telescope and the Hubble Space Telescope where we proved that both detailed abundance and metallicity analyses are possible for star clusters at distances of several Mpc. Local contact: V. Lebouteiller; organization: V. Lebouteiller |
Tuesday May 21 10:00 | O. Porth (University of Amsterdam)
Behind the image: first analysis of the black hole shadow in M87
[click here for abstract] For the first time, horizon scale structure around a supermassive black
hole was imaged with the EventHorizonTelescope. In this talk, I will
discuss the physical interpretation of the ring-like structure emerging
in the center of the galaxy M87. To compare the observations with
theoretical expectations, a library of ~60000 theoretical images was
obtained from 3D GRMHD simulations with different black hole spins,
masses and orientations. The data is consistent with most simulations
of a radiatively inefficient accretion flow and yields a black hole
mass of 6.5x10^9 Msun, in excellent agreement with the stellar dynamical
measurement. Further firm parameter constraints are currently thwarted
by the stochastic nature of the underlying models as well as the
uncertain modeling of electron physics in near collision-less regimes.
More constraints are set by including multi-wavelength data and by using
limits on the jet power. I will also briefly discuss implications to alternatives to GR and
future prospects for physics with the EHT. Local contact: M. Bugli; organization: M. Bugli |
Tuesday June 4 10:00 | C. Baruteau (IRAP)
Observational predictions of the presence of giant planets in the dust’s radio emission of protoplanetary discs
[click here for abstract] The classical picture of protoplanetary discs forming smooth, continuous structures of gas and dust has been challenged by the growing number of spatially resolved observations. These observations indicate that radial discontinuities and large-scale asymmetries may be common features of the emission of protoplanetary discs, which are often interpreted as signatures of the presence of (unseen) planetary companions. During this seminar, I will report our recent and ongoing efforts to predict the dust’s radio emission in protoplanetary discs due to the presence and orbital evolution of giant planets, through gas+dust hydrodynamical simulations post-processed with dust radiative transfer calculations. I will show via these models that recent ALMA observations strongly suggest the presence of several planets in the discs around MWC 758 and HD 169142. Local contact: S. Mathis, A. Astoul; organization: V. Lebouteiller |
Monday June 17 11:00 Salle Galilée | Special seminar / séminaire exceptionnel M. Katsuragawa (Takahashi Laboratory, Kavli IPMU, University of Tokyo)
Time-dependent hydrodynamic model of X-ray emitting plasma in evolved SNRs
[click here for abstract] Recently, X-ray observations revealed that some of evolved supernova remnants (SNRs) have plasmas in which the recombination process becomes more dominant than the ionization process. In most of these SNRs having the recombining plasma (RP), association of molecular and atomic clouds are observed. This implies that the evolution of SNRs are considered to be deeply related to the environment of the ambient gas, though they are not fully understood.
In order to study physical and astrophysical causes of the formation of the RP in evolved SNRs, we develop a new framework that provides both X-ray spectra and images of evolved SNRs with an age of > 104 yr. Our model calculates the time evolution of temperatures of electron and ions, which are not considered in previous plasma models, based on a one-dimensional Lagrangian hydrodynamics simulation. We include physical processes of shock heating, energy exchange by Coulomb interaction, radiative cooling and evolution of ionization states. The spectra are composed of bremsstrahlung and emissions by atomic transition of major elements calculated from atomic properties of AtomDB.
Since effects of the surrounding environment of SNRs is important in their evolution, we investigate the relation between plasma states in SNRs and interstellar medium (ISM) density using our model by changing ISM density (1, 3, 10, and 30 cm-3). In our simulation, the RP is naturally produced in evolved SNRs (~ 104 yr) which exploded in the dense ISM. We characterize spectra by the electron temperature and ionization temperature that is an indicator of describing the ionization state. As a result of comparing these temperatures of our model with the observations, we successfully demonstrate that the time evolution of ionization and recombination are in excellent agreement with the observed values. Our model holds promising application for future X-ray missions with a high resolution spectrometer. Local contact: O. Limousin, D Renaud; organization: M. Galametz |
Tuesday June 18 10:00 | Gianpiero Mangano (INFN Napoli)
Neutrino Physics with the PTOLEMY project
[click here for abstract] The PTOLEMY project aims to develop a scalable design for a Cosmic Neutrino Background (CNB) detector, the first of its kind and the only one conceived that can look directly at the image of the Universe encoded in neutrino background produced in the first second after the Big Bang. The scope of the work for the next three years is to complete the conceptual design of this detector and to validate with direct measurements that the non-neutrino backgrounds are below the expected signal from the Big Bang. In this talk I discuss in details the theoretical aspects of the experiment and its physics goals. In particular, I mainly address three issues. First the sensitivity of PTOLEMY to the standard neutrino mass scale. I then consider the perspectives of the experiment to detect the CNB via neutrino capture on tritium as a function of the neutrino mass scale and the energy resolution of the apparatus. Finally, I consider an extra sterile neutrino with mass in the eV range, coupled to the active states via oscillations, which has been advocated in view of neutrino oscillation anomalies. This extra state would contribute to the tritium decay spectrum, and its properties, mass and mixing angle, could be studied by analyzing the features in the beta decay electron spectrum. Local contact: V. Pettorino; organization: M. Bugli |
Tuesday June 25 10:00 | K. Kosack (DAp)
Searching for PeV accelerators with Very-High-Energy Gamma Rays
[click here for abstract] From the cosmic-ray spectrum, we know that there must be objects in our galaxy that can accelerate particles to above PeV energies, but it's not clear what they are. Very-High-Energy gamma-rays (E>100 GeV to >100 TeV) provide a useful tool for searching for these accelerators, since they provide a view of non-thermal photon emission from the sites where particles are accelerated. I will present an overview of the problem, how we are using telescopes like HESS (and later CTA) to search for these "PeVatrons" and what difficulties have been encountered. Finally, I will show the latest results, including evidence for an acceleration event in the Galactic Center. Local contact: V. Lebouteiller; organization: V. Lebouteiller |
Tuesday July 2 10:00 | Stefano Camera (Università Degli Studi di Torino)
Radio cosmology and the SKA
[click here for abstract] In this talk, I shall review the most peculiar aspects of
cosmology in the radio band, with a special focus on the Square
Kilometre Array (SKA) radio-telescope and its pathfinders. I shall
present the main radio probes that can be exploited for late-time
cosmology: continuum and 21-cm line galaxy surveys, neutral hydrogen
intensity mapping, and even weak lensing cosmic shear at radio
frequencies. Moreover, I shall also discuss the added value of multi-
wavelength synergies, presenting some show-case example of the power of
radio-optical cross-correlations to test the fundaments of the
concordance cosmological model, such as the nature of dark matter and
dark energy, or tests of inflation and gravity. Local contact: V. Pettorino; organization: V. Pettorino |
Thursday July 11 10:00 | Special seminar / séminaire exceptionnel Sherry Suyu (MPA)
Cosmology with Gravitational Lens Time Delays
[click here for abstract] Strong gravitational lenses with measured time delays between the multiple images can be used to determine the Hubble constant that sets the expansion rate of the Universe. Measuring the Hubble constant is crucial for inferring properties of dark energy, spatial curvature of the Universe and neutrino physics. I will describe techniques for measuring the Hubble constant from lensing with a realistic account of systematic uncertainties. A program initiated to measure the Hubble constant to <3.5% in precision from strong lenses is in progress, and I will present the latest results and their implications. Search is underway to find new lenses in imaging surveys. An exciting discovery of the first strongly lensed supernova offered a rare opportunity to perform a true blind test of our modeling techniques. I will show the bright prospects of gravitational lens time delays as an independent and competitive cosmological probe. Local contact: M. Kilbinger; organization: M. Bugli |
SUMMER BREAK | |
Tuesday September 10 10:00 | Sandra Treviño Morales (Chalmers University, Sweden)
Dynamics and fragmentation in Galactic filamentary structures
[click here for abstract] The study of the filamentary structures in massive star-forming regions
is undergoing a revolution, thanks in large part to the unprecedented
high angular resolution and sensitivity that ALMA provides. We have used
ALMA to conduct an observational study of two massive filaments and a
hub-filament system with the main goal of building a picture of their
global dynamical properties and fragmentation. We present the results
for the Monoceros R2 (hereafter MonR2) molecular cloud, one of the
nearest and clearest examples of a hub-filament system. The central hub
hosts a cluster of massive protostars associated with an expanding HII
region, where a number of filaments are converging. We have estimated
total the mass accretion rate along the filaments on the order of 10^(-
3) Msun/yr. Inside the central hub, the filaments appear twisted forming
a spiral-like structure, with signs of rotation and infall motions.
Overall, the hub-filament system in MonR2 suggests a scenario of non-
isotropic global collapse, forming a massive stellar cluster. We also
present our results for G357, which is a massive filament similar to the
integral shaped filament (ISF) in Orion A, but shows remarkably low star
formation activity. The comparison of the fragmentation and dynamics of
G357 and the ISF enables us to address the early evolution of massive
filaments. Local contact: P. Didelon; organization: V. Lebouteiller |
Tuesday September 24 10:00 | Eiichiro Komatsu (MPIA)
Finding Cosmic Inflation
[click here for abstract] The cosmic microwave background (CMB) research told us a remarkable story: the structure we see in our Universe such as galaxies, stars, planets, and eventually ourselves originated from tiny quantum fluctuations generated in the early Universe. With the WMAP we have confirmed many of the key predictions of inflation including flatness and statistical homogeneity of our Universe, Gaussianity and adiabaticity of primordial density fluctuations, and a small but non-zero deviation from the scale-invariant spectrum of density fluctuations. Yet, the extraordinary claim requires extraordinary evidence. The last prediction of inflation that is yet to be confirmed is the existence of primordial gravitational waves whose wavelength can be as big as billions of light years. To this end we have proposed to JAXA a new satellite mission called LiteBIRD, whose primary scientific goal is to find signatures of gravitational waves in the polarisation of the CMB. In this presentation we describe the current state of affairs regarding our understanding of the early Universe, physics of polarisation of CMB, and the LiteBIRD mission. Local contact: V. Pettorino; organization: M. Bugli |
Thursday September 26 10:00 | Special seminar / séminaire exceptionnel Daniela Calzetti (UMass)
Linking the Scales of Star Formation
[click here for abstract] Formulating a Predictive Theory of Galaxy Evolution requires understanding star formation and its dependence on the local environment, spanning the scales from individual stars to kpc–size structures. The physical conditions within galaxies determine the formation of stars, star clusters, and larger structures, and their subsequent evolution. In turn, these structures, through feedback, affect the evolution of the host galaxy. HST observations of external galaxies have enabled the characterization of the young stellar populations with unprecedented accuracy and detail, thus aiding the census and description of those populations. These observations are being used to quantify the spatial distribution and clustering of young stars, and investigate the impact and imprint of the physical conditions of both the local and global environment on the formation and evolution of the multi-scale structures. I will concentrate mainly on the results of the Legacy ExtraGalactic UV Survey (LEGUS), an HST Treasury programs that is investigating these issues using multi-color imaging, from the near-UV to the I, of a sample of nearby galaxies. I will also briefly introduce successor programs that promise to expand our understanding of star formation and feedback on galactic scales. Local contact: E. Daddi; organization: M. Galametz |
Tuesday October 8 10:00 | Jaime Pineda (MPE Garching)
Following the gas from dense core to protostellar disk
Local contact: A. Maury; organization: M. Galametz |
Tuesday October 22 10:00 | Special seminar / séminaire exceptionnel Vacances de la Toussaint Michael Meyer (webpage) (University of Michigan)
Blazing a trail: towards imaging super-earths from the ground and space
[click here for abstract] The discovery and characterization of extrasolar planets has been data-driven: clearly there
are more things in heaven and earth than are dreamt of in our philosophies. As the demographics of the myriad diverse systems becomes known, we begin to piece together the larger story of their formation and evolution. Ultimately, we seek to understand the prospects for life elsewhere in the Universe. In addition to this scientific quest, ‘exploration’ also plays a role. In particular, the nearest star systems provide an opportunity to explore in detail strange new worlds. The announcement of a planet < 10 Mearth in the liquid-water zone of Proxima Centari sent shock waves through the community. What is the nature of this planetary system found in our own galactic backyard? Could it be habitable? Here we will review plans to try to image small planets from the ground in thermal emission around the nearest stars, including development of a new generation of mid-infrared detectors with high quantum efficiency, low noise, and suitable for ground-based use, as well as instruments planned for the next generation extremely large telescopes such as METIS on the E-ELT. We will also discuss the power of imaging planets both in reflected light and thermal emission, and the possibility of detecting the greenhouse effect in a world outside the Solar System. Local contact: E. Pantin; organization: M. Galametz |
Tuesday November 5 10:00 | Cancelled / séminaire annulé |
Tuesday November 19 10:00 | Recent hiree seminar / séminaire arrivant récent J. Guilet (DAp)
The MagBURST project: Magnetar birth as engine of extreme stellar explosions
[click here for abstract] The birth of a neutron star with an extremely strong magnetic field, called a magnetar, has emerged as a promising scenario to power a variety of outstanding explosive events. This includes gamma-ray bursts, supernovae with extreme kinetic energies called hypernovae and super-luminous supernovae. The origin of these extreme magnetic fields (of the order of 10^15 Gauss) is not fully understood yet and requires an amplification over several orders of magnitude during the formation of the neutron star.
I will describe our current understanding of the physical processes that may lead to this magnetic field amplification and the consequences for the explosion properties. Local contact: [-]; organization: M. Bugli |
Tuesday December 3 10:00 | Shu-Ichiro Inutsuka (Nagoya University)
Filament Paradigm and Galactic Star Formation
[click here for abstract] Recent observations have emphasized the importance of the formation and
evolution of magnetized filamentary molecular clouds in the process of
star formation. Theoretical and observational investigations have
provided convincing evidence for the formation of molecular cloud cores
by the gravitational fragmentation of filamentary molecular clouds.
Thus, the mass function and rotations of molecular cloud cores should be
directly related to the properties of the filamentary molecular cloud,
which determines the initial size and mass distribution of a
protoplanetary disk around a protostar created in a core. In this talk I
explain our current understanding of the star formation processes in the
Galactic disk, and summarize various processes that are required in
describing the filamentary molecular clouds to understand the star
formation rate/efficiency, the stellar initial mass function, and the
angular momentum distribution of protoplanetary disks in their early
evolutionary phase. Local contact: V. Valdivia, P. André; organization: M. Galametz |
Wednesday December 4 11:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Mélanie Chevance (University of Heidelberg, Astronomisches Rechen-Institut Zentrum fuer Astronomie)
A systematic characterisation of the evolutionary cycling between molecular clouds, star formation, and feedback in nearby galaxies
[click here for abstract] Star formation is one of the main drivers of galaxy evolution, but an understanding of this process remains elusive. This is caused by a lack of systematic observational constraints on cloud scales. Star formation in galaxies is expected to be highly dependent on the galactic structure and environment, as it results from a competition between mechanisms such as gravitational collapse, shear, spiral arm passages, cloud-cloud collisions, and feedback. A statistically representative sample of galaxies is therefore needed to probe the wide range of conditions under which stars form. I will present the first systematic characterisation of the evolutionary timeline of molecular clouds and star-forming regions, derived by applying the statistical method of Kruijssen & Longmore (2014) and Kruijssen et al. (2018) to homogeneous ALMA + optical observations at 50 pc resolution of a large sample of star- forming disc galaxies out to 17 Mpc (obtained in the context of the PHANGS collaboration). This method uses the multi-scale nature of the star formation relation to constrain the timeline and efficiencies for star formation and feedback on the cloud scale, across a wide variety of galactic environments. I will show that star formation is regulated by efficient stellar feedback, driving GMC dispersal on short timescales (1-5 Myr) due to radiation and stellar winds, prior to supernova explosions. This feedback limits GMC lifetimes to about one dynamical timescale (10-30 Myr), with integrated star formation efficiencies of only a few percent. Our findings reveal that galaxies consist of building blocks undergoing vigorous, feedback-driven lifecycles, that vary with the galactic environment and collectively define how galaxies form stars. These observations settle a long-standing question on the multi-scale lifecycle of gas and stars in galaxies, and open up the exciting prospect of studying cloud-scale star formation and feedback in galaxies across cosmic time. Local contact: S. Madden; organization: S. Madden |
Monday December 16 11:00 | H. Tsunemi (University of Osaka)
All-sky maps of the diffuse X-rays from 0.7 keV to 4 keV obtained by MAXI/SSC
[click here for abstract] MAXI (Monitor of All-sky X-ray Imager) was launched in 2009
and installed on the International Space Station.It consists
of the Gas Slit Camera (GSC) and the Solid-State Camera. The
GSC, gas proportional counter array, covers the energy range
from 2.0kev to 30keV while the SSC, CCD cameras, covers the
energy range from 0.7keV to 7keV. In the seminar, I will
focus on the SSC. The SSC consists of 32 CCDs in total with a
mechanical slit. The CCD performance is gradually degrading
in orbit due to its harsh radiation environment. I will
report on the diffuse X-ray background maps obtained in
energies of 0.7--1.0, 1.0--2.0, and 2.0--4.0 keV,
respectively. They are the first ones that were derived with
a solid-state instrument.
The diffuse soft X-ray background was discovered in the past
by using sounding rocket experiments and studied in detail by
ROSAT All Sky Survey (RASS). After that, we learnt that the
solar wind charge exchange (SWCX) was a nuisance in X-ray
astronomy, particularly below 1.0keV. The SWCX is believed to
depend on the solar activity and seriously affects the diffuse
X-ray background. RASS was done in high solar activity while
SSC was done in low solar activity separating about 20 years.
Our result shows a good correlation with that by RASS. Local contact: A. Meuris; organization: A. Meuris |
Tuesday December 17 10:00 | N. Peretto (Cardiff University)
From the structure of molecular clouds to the formation of massive (proto)stars
[click here for abstract] Star formation is a complex process that involves dusty gaseous structures covering orders of magnitude in spatial scales and gas densities. How the physical properties and dynamical evolution of these structures relate to a particular star formation event is yet to be fully uncovered. In the past decade, some progress has been made on linking the properties of low-mass star-forming cores to those of the interstellar filaments in which they most often form. On the other hand, there is also a growing body of evidence suggesting that the reservoirs from which massive (proto)stars accrete gas from are typically much larger than those for low-mass protostars. Trying to determine what physical process fixes the properties of these mass reservoirs, and finding out how they evolve towards the formation of individual stars and stellar clusters is at the heart of current star formation research. In this context, I will present recent observational studies aiming at understanding how gas flows from the scale of a giant molecular cloud to individual massive-star forming cores, and how feedback from recently formed OB stars affect their parent molecular cloud. I will discuss how the corresponding findings impact our current knowledge on molecular cloud structure and dynamical evolution of dense star-forming clumps. Local contact: V. Lebouteiller; organization: V. Lebouteiller |
2018 | |
Tuesday January 9 10:00 | Claudia Maraston (webpage) (Institute of Cosmology and Gravitation - University of Portsmouth)
Stellar Population Models: interpreting the bright side of the Cosmos
[click here for abstract] The Universe is infinitely large and dramatically dark, apparently dominated by unknown components which make up most of the matter/energy budget. Fortunately, that tiny 4.6% of baryons act under the robust laws of nuclear physics and stellar evolution, theories which we can use to understand the bright side of the Universe. In this talk I shall discuss interpretative models for distant galaxies and illustrate the historical path that paved the way to modern calculations. I shall then use those models to infer conclusions on the formation and evolution of the most massive galaxies. Local contact: E. Daddi; organization: K. Augustson |
Tuesday January 23 10:00 | Nina Hatch (University of Nottingham)
The formation of galaxy clusters
[click here for abstract] Distant galaxy clusters are powerful laboratories for observing the hierarchical growth of large-scale structure, constraining cosmological parameters, and for studying the formation of galaxies. However, distant (z>1.5) clusters are extremely rare and faint, so locating and studying them poses a significant observational challenge. In this seminar, I will review the theory of cluster formation and present recent advances we have made in detecting and studying distant galaxy clusters. Local contact: A. Le Brun; organization: V. Lebouteiller |
Monday January 29 10:00 | Special seminar / séminaire exceptionnel Jason Rhodes (JPL)
NASA's Next Astrophysics Flagship: The Wide Field Infrared Survey Telescope (WFIRST)
[click here for abstract] The top recommendation for a large space mission in the US 2010 Decadal Survey was the Wide Field Infrared Survey Telescope (WFIRST). Similarities in hardware requirements between proposed dark energy, exoplanet microlensing, and near infrared surveyor missions allowed for a single mission that would accomplish all three goals. The gift of an existing 2.4 meter telescope to NASA by another US government agency allowed for the addition of a coronagraph that will take images and spectra of nearby exoplanets; this instrument will be a technological stepping stone to imaging other Earths in the 2030s. I will give an overview of WFIRST's proposed instrumentation, science goals, and implementation plan. Local contact: J. L. Starck; organization: V. Lebouteiller |
Tuesday February 6 10:00 | Sambit Roychowdhury (IAS, Orsay)
Dwarf galaxies, and the star formation relation in the HI dominated regime
[click here for abstract] Star forming dwarf galaxies are by far the most abundant type of galaxies in the
local Universe. They also lie at the base of the hierarchical structure formation
ladder - as they later merge into larger halos. Understanding the baryon cycle in
these galaxies is critical towards solving the major mismatches between
observations and simulations of structure formation.
Empirically constraining the relationship between gas and star formation in these
galaxies remains challenging though, given their faintness across all observed
wavelengths. I will describe our efforts to empirically quantify the relation between
gas and star formation using the 21 cm emission line from atomic hydrogen (HI)
as a tracer of gas, not only in dwarfs but also in the HI-dominated outskirts of spirals. Local contact: S. Madden; organization: M. Galametz |
Tuesday February 20 | Vacations / Vacances |
Tuesday March 6 10:00 | Mara Salvato (MPE, Garching)
The eROSITA Surveys and the follow-up
[click here for abstract] eROSITA (extended ROentgen Survey with an Imaging Telescope Array) is the core instrument on the Russian/German Spektrum-Roentgen-Gamma (SRG) mission which is current scheduled for launch in 2018.
In the soft band (0.5-2 keV), the deep All-sky survey will be 30 times more sensitive than the previous ROSAT All-sky survey, while the first ever true all-sky survey will be mapped in the hard band (2-8 keV).
The design driving science is the detection of large samples of galaxy clusters to redshifts z > 1, in order to study the large scale structure in the Universe and test cosmological models including Dark Energy.
In addition, eROSITA is expected to yield a sample of around 3 million active galactic nuclei, which is bound to revolutionize our view of the evolution of supermassive black holes and their impact on the process of structure formation in the Universe.
Finally, the survey will also provide new insights into a wide range of astrophysical phenomena, including neutron stars and pulsars, X-ray binaries, active stars and diffuse emission from supernova remnants. The talk reports on the status of eROSITA and its scientific prospects. In the end, I will also briefly discuss how the German eROSITA consortium is activated for ensuring an adequate follow-up of the sources to be discovered. Local contact: E. Le Floc'h; organization: M. Galametz |
Tuesday March 20 10:00 | Recent hiree seminar / séminaire arrivant récent Samuel Farrens (CEA/DAp)
Multidisciplinary Data Acquisition and Image Processing Tools (That Make Your Life Easier)
[click here for abstract] The ability to obtain high quality data in a short amount of time or indeed to recover high resolution images from from incomplete blurred and noisy data can significantly improve the results of experiments potentially leading to new and exciting scientific discoveries. Mathematical techniques such as compressed sensing and sparse regularisation provide these benefits for many sources of data in a variety of different fields. Compressed Sensing for Magnetic Resonance Imaging and Cosmology (COSMIC) is a CEA DRF funded project that brings together MRI experts at NeuroSpin with astronomical image analysis experts at CosmoStat in order to develop an open source software package called PySAP (Python Sparse data Analysis Package) that implements these signal processing tools. This talk will provide a brief introduction to the types of problems encountered in acquiring/processing MRI and astrophysical images and demonstrate how the tools provided in PySAP can be beneficial. Local contact: [-]; organization: K. Augustson |
Tuesday April 3 10:00 | Recent hiree seminar / séminaire arrivant récent Marc-Antoine Miville-Deschênes (Laboratoire AIM)
The clockwork of star formation
[click here for abstract] The formation of stars is a fundamental aspect of how matter evolves in the Universe. It dictates timescales, chemical and structure evolution of baryons. It is the respiration of galaxies; star formation makes galaxies “boil”, bubble and fragment. Without it the Universe would have ended up in a sterile collection of gravitational singularities. Star formation creates structures as a result of specific non-linear physical processes. In that respect, a galaxy is a complex, self-organized system. This complexity is revealed by the multi-scale and multi-phase nature of the interstellar medium. This talk will be about the use of multi-wavelength, and especially hyper-spectral data, to uncover aspects of the energy and matter cascade of the interstellar medium of the Milky Way. I will present how such data (dust, CO, 21 cm) and their comparison to numerical simulations, can be used to get a clearer view of the evolution of diffuse matter in a galaxy like the Milky Way. In particular I will present recent results on the use of dust scattering to trace the cascade of the ISM cascade down to very small scales, as well as our current work on the analysis of large 21 cm datasets to uncover the first steps of the formation of cold and dense structures in the diffuse ISM. Local contact: [-]; organization: M. Galametz |
Tuesday April 17 | Vacations / Vacances |
Tuesday May 1 | Holiday / Jour férié |
Tuesday May 15 10:00 | Edward B. Jenkins (Princeton University)
The Condensation of Gas-Phase Elements onto Interstellar Dust Grains
[click here for abstract] Over the past 45 years, investigations of ultraviolet absorption features in stellar spectra have revealed that most of the heavy elements in the interstellar medium are depleted from the gas phase to values well below solar or B star reference abundances. The strengths of such depletions reveal the composition of dust grains in space, and they can be characterized by a limited set of parameters that are closely linked to the average gas densities and the condensation temperatures of the elements. Two outstanding mysteries remain: one is the fact that the depletion of oxygen exceeds that needed for forming silicates or metallic oxides, and the other is that the chemically inert element krypton shows some depletion. When we observe absorption features to derive the element abundances in distant galaxies, we must understand how to correct for depletions by using the patterns found in our Galaxy or the Small Magellanic Cloud as examples. Comparisons of interstellar abundances to those found in circumstellar disks may help us to understand better the replenishment and dispersal of gaseous matter in such systems. Local contact: M. A. Miville-Deschênes; organization: M. Galametz |
Tuesday May 29 10:00 | Sébastien Charnoz (IPGP)
Saturns rings as seen by Cassini, and the life at the edge of the Roche limit
[click here for abstract] In this presentation I will talk mainly about Cassini discoveries and
results concerning the outer edge of Saturn’s main rings, that is a very
peculiar place called the «Roche limit».
In this region, accretion processes are balanced by tidal forces
producing a variety of time variable structures because of the endless
competition of these two processes.
Temporary moons, ringlets regularly destroyed by moonless interactions,
a complex interplay have been discovered. I will talk about mainly about
of strange physics of this region and show that moons and rings are the
two sides of a same system. Many discovered processes are similar to
still unobserved mechanisms invoked for planetary formation.
The discussion will also extend to the formation of short-period planets
around white dwarves, that can be explained by exactly the same
processes. Local contact: K. Augustson; organization: K. Augustson |
Tuesday June 12 10:00 | Tomoki Nakamura (Tohoku University)
Formation process of framework structure of carbonaceous material in ultra-carbonaceous micrometeorites
Local contact: P. Hennebelle; organization: V. Lebouteiller |
Tuesday June 26 10:00 | Guy Davies (webpage) (University of Birmingham)
Stellar ages from asteroseismology: The Galactic thick disk
Local contact: K. Augustson; organization: K. Augustson |
Friday July 6 10:00 | Cancelled / séminaire annulé Melanie Johnston-Hollitt (Curtin Institute of Radio Astronomy)
[TBA]
Local contact: G. Pratt; organization: S. Pires |
SUMMER BREAK | |
Monday September 10 14:00 | Special seminar / séminaire exceptionnel Johan Richard (webpage) (CRAL, Lyon)
Blue-MUSE: a blue-optimised large field integral-field spectrograph
[click here for abstract] The Multi-Unit Spectroscopic Explorer (MUSE) is an integral field
spectrograph with unique capabilities on the Very Large Telescope. With
its high sensitivity and by providing a complete view of the optical
spectrum over 1 arcmin2 it has been a tremendous breakthrough in the way
galactic and extragalactic observations are performed. The success of
MUSE calls for new ideas for the next generation of IFUs, and I will
present the concept of a BlueMUSE. With a field of view increased up to
1.4 x 1.4 arcmin2 and a higher spectral resolution, BlueMUSE is covering
wavelengths down to the atmospheric cut-off (350 nm). The current
instrumental concept currently being investigated includes the use of
curved detectors. BlueMUSE opens up a new range of galactic and
extragalactic science cases allowed by its specific capabilities:
including for example the study of young stars, the properties of the
gas in the circumgalactic medium, and high redshift clusters. Local contact: E. Daddi; organization: V. Lebouteiller |
Tuesday September 11 10:00 | Nick Kaiser (ENS)
Gravitational redshifts in clusters of galaxies
[click here for abstract] Wojtak, Hansen and Hjorth and others have measured the long-predicted gravitational redshift of light escaping from galaxy clusters.
The effect is very small, corresponding
to a velocity shift of only about 10 km/s, but the result appears to be fairly robust and seemed to be in good agreement with general relativity predictions and possibly in conflict with some alternative theories. The effect was initially
imagined to be a simple astronomical analogue of the famous terrestrial
Pound and Rebka experiment that verified Einstein's theoretical
prediction. However, it was soon realised that the physics of this
effect is considerably more complex. As I shall describe, there are
actually three other contributions to the measured signal that need
to be taken into account. I shall describe recent attempts to model
these effects using N-body experiments, and how this effect may be
useful for testing alternative theories of gravity. Understanding this apparently simple effect reveals some subtleties in special relativity and also
sheds light on the interpretation of redshifts in cosmology. Local contact: K. Augustson; organization: K. Augustson |
Friday September 21 10:00 | Special seminar / séminaire exceptionnel Nissim Kanekar (webpage) (NCRA, India)
Cold Gas at High Redshifts
[click here for abstract] The gas mass and star formation rate of damped Lyman-alpha absorbers (DLAs), a population of
high-redshift absorption-selected galaxies, have been open questions in the field of galaxy
evolution for more than three decades. This talk will describe new results from ALMA
searches for CO and CII-158 micron emission from a sample of DLAs over a wide range of
redshifts, z~0.5-4.2. These are the first CO and CII-158 micron detections in DLA host
galaxies, providing a new window on physical conditions in absorption-selected galaxies,
and yielding a new tool to identify DLA host galaxies at high redshifts. Local contact: M. Arabsalmani; organization: V. Lebouteiller |
Tuesday September 25 10:00 | M. Haywood (GEPI)
Dissecting a Milky Way-like galaxy from the inside
[click here for abstract] In the local universe, a star has a higher probability of being in a
galaxy of the mass of the Milky Way
than in any other galaxy, and we have the opportunity to be able to
study one such galaxy from the inside.
We can, in particular, study its stellar mass growth with time, and
understand how each
of the known stellar populations is connected to this mass growth
history.
While much is expected from the analysis of the Gaia data in this
regard, it is safe to say that a change of paradigm
concerning the stellar populations of our Galaxy is already under way,
due in particular to important
results coming from the analysis of recent spectroscopic surveys. I will
present and discuss some
of these results. Local contact: [-]; organization: M. Bugli |
Tuesday October 9 10:00 | J.-P. Bernard, A. Mangilli (IRAP)
[2-in-1 seminar: science+instrumentation] Polarized emission from dust with the stratospheric balloon PILOT
[click here for abstract] PILOT is an experiment with a stratospheric balloon designed to measure
the thermal dust polarized emission at 240 microns which enables to
measure the geometry of the magnetic field in the Interstellar Medium
using multiplexed bolometric detectors developed by CEA for the Herschel
PACS mission. In this talk, we will describe the instrument and its
performances measured during the first two flights that took place in
2015 and 2017 from Canada and form Australia respectively.
We will discuss the first scientific results on the geometry of the
magnetic field in the central molecular zone of our Galaxy. We will
insist on the strict control of systematic instrumental effects crucial
for this type of measurements and the associated difficulties in the
data treatment and calibrations. Finally, we will talk of the future
PILOT project and in particular its evolution to COPILOT designed to
measure the integrated emission of the C+ line in the ISM and to become
a demonstrator of the detection chain for the SPICA-POL instrument.
Local contact: L. Rodriguez; organization: M. Galametz |
Tuesday October 23 10:00 | Special seminar / séminaire exceptionnel Annop Wongwathanarat (MPA Garching)
Towards linking core-collapse supernova simulations with observations
[click here for abstract] With recent advances in numerical techniques and computing power theoretical modeling of a core-collapse supernova (CCSN), a cataclysmic event marking the end of the lifetime of a massive star, has become feasible in three spatial dimensions.
In this talk, I will review recent progress which have been made in modeling the long-term evolution of CCSN explosion starting from the collapse and explosion phase until the SN ejecta transform into the early SN remnant phase.
I will discuss how simulation results can be compared with observables such as explosion asymmetries, element distributions, SN light curves, and pulsar kick velocities that are obtained from recent observations of SN and SN remnants. Local contact: J. Guilet, T. Foglizzo, F. Acero; organization: M. Bugli |
Tuesday November 6 10:00 | D. Götz, A. Meuris (DAp)
[2-in-1 seminar: science+instrumentation] The MXT project at DAp: building an X-ray camera for time domain astrophysics
[click here for abstract] We will present the science goals of the SVOM mission and how the Microchannel X-ray Telescope (MXT) will contribute to reach them. SVOM a a Sino-French mission (to be launched by the end of 2021) dedicated to Gamma-Ray Bursts and transient sky studies, and MXT is part of the payload that will be delivered by France. It is a focussing soft X-ray (0,3-6 keV) telescope, which is based on a new optical concept called "Lobster-Eye", coupled to a low noise pn CCD detector. The Irfu/DAp carries the scientific responsibility of the entire telescope, and is in charge of the development of the camera, including all the functions around the detector to get optimal performance. We will present the design of the camera, the associated challenges and the recent achievements. Local contact: [-]; organization: V. Lebouteiller |
Tuesday November 20 10:00 | N. Palanque-Delabrouille (Irfu/DPhP)
Structures in the cosmos: what they tell us about neutrinos and warm dark matter
[click here for abstract]
The Sloan Digital Sky Survey (SDSS) has been mapping the sky for almost a decade, providing crucial information on the dark universe though measurements of BAO and RSD (redshift space distortions). As one of the SDSS components, the Lyman-alpha forest survey is a rich source of information. Because it gives access to small (tens of Mpc) scales, it allows one to probe the impact on the clustering of matter of neutrino mass and warm dark matter. I will briefly recall the major goals of SDSS, and introduce the quasar survey where the Lyman-alpha forest is measured. I will then present one of the strongest constraints on neutrino mass from a combination of CMB and Lyman-alpha data. Finally, I will show how the study of clustering in the Lyman-alpha forest can also lead to competitive constraints on warm dark matter and on several models of keV sterile neutrinos. Local contact: [-]; organization: M. Galametz |
Tuesday December 4 10:00 | no seminar - HCERES Irfu |
Tuesday December 18 11:00 | V. Masson (webpage) (LSCE)
Key points of the IPCC Special Report on Global warming of 1.5°C
[click here for abstract] In 2015, at COP21, governments invited the IPCC to prepare this special report. It was approved by delegates from all governments in October
2018, on the basis of the assessment performed by 91 authors from 40
countries, with 133 contributors, of 6000 publications, after 3 rounds
of review (1131 reviewers, more than 42 000 review comments).
This report provides the current state of global warming, with 1°C due
to human activities; the consequences of an additional half a degree or
one degree of global warming; the greenhouse gas emission trajectories
consistent with stabilisations at 1.5°C or 2°C; the systems transitions,
with an assessment of 6 dimensions of feasibility; the multiple
intersections with sustainable development goals.
This report is so stimulating that governements could not find words to
receive it. In December 2018, at COP24, four of them (Saudi Arabia,
Kuweit, USA and Russia) refused to welcome it. The COP24 decision
expresses its appreciation for the work done, welcomes the timely
completion of the report, and invites parties to make use of it... Local contact: M. Galametz; organization: M. Galametz |
2017 | |
Wednesday January 11 10:00 | Rychard Bouwens (Leiden University)
Observational Studies of Very High-Redshift Galaxies
Rychard Bouwens is an associate professor at Leiden Observatory. He has been a core author of three papers since 2015 which have successively broke the spectroscopic record for highest-redshift galaxy, won the Pastoor-Schmeitsprijs voor de Sterrekunde in 2013, and has been one of the leading experts on research on high-redshift galaxies for the last 10 years. [click here for abstract] Over the last few years, enormous progress has been made probing galaxies in the first two billion years thanks to the incredible capabilities of the Hubble and Spitzer Space Telescopes. Already, more than 1500 probable galaxies are known at redshifts above z~6, and now the current frontier is at z~9-10, with 50 plausible galaxy identifications to date, and a credible spectroscopic redshift determination to z=11.1. Deriving physical properties for these distant galaxies is also an important frontier, and progress has been impressive even as early as z~7-8, with probes of nebular emission-line strengths and specific star formation rates to z~8.5 and new constraints on dust-enshrouded star formation at z>~2 from ALMA. One exciting emerging frontier has been probes of ultra-faint galaxies in the early universe with the Hubble Frontier Fields (HFF) program using gravitational lensing and long exposures. To guarantee the best results, accurate determinations of both the size distribution and lensing models are required. In this colloquium, I describe new work on the HFFs, while surveying many current highlights on early galaxy research. Local contact: [-]; organization: [-] |
Tuesday January 24 10:00 | Jean-Michel Désert (University of Amsterdam)
Characterizing Exoplanets’ Atmospheres to Unveil Planetary Origins, Climate and Habitability
Jean-Michel Désert is an assistant professor at the University of Amsterdam in the Netherlands. He works on exoplanets and leads observational campaigns to obtain multi-wavelength observations of transiting exoplanet atmospheres to learn about their composition and origins. He is the PI of the current largest survey of exoplanet atmospheres with ground-based telescopes (Gemini/GMOS). He was recently awarded an ERC starting grant in order to employ novel techniques to probe exoplanet atmospheres. [click here for abstract] Exoplanet detection surveys over the last twenty years have revealed a surprising diversity of planets orbiting other stars— this revolution is fuelled by fundamental questions about the place of the Earth and the Solar System in the Universe. How do planets form? What range in architectures of planetary systems exist? How does our Solar System fit into this context? And perhaps the most exciting of all: do other life-bearing planets exist?
The study of exoplanet atmospheres is the next step in leveraging exoplanetary detections. This is because a planet’s atmosphere provides a fossil record of its primordial origins and controls its fate, size, appearance, and ultimately its habitability. In this context, I present comparative exoplanetology programs that aim at characterising planetary systems transiting nearby stars through the observations of their atmospheres. Our findings on the atmospheric composition and physical properties provide insights into the formation and evolution of planetary systems and enhance our understanding of our own Solar System’s formation. Finally, I also present strategies for probing habitable exoplanet atmospheres in the quest for bio-signatures. Local contact: V. Lebouteiller; organization: V. Lebouteiller |
Friday January 27 14:15 Salle Kepler | Group seminar open to everybody / séminaire de groupe ouvert à tous Vivien Parmentier (NASA Sagan Fellow, University of Arizona)
Composition and distribution of clouds in exoplanets: an L/T-like transition for hot Jupiters?
[click here for abstract] Over a large range of equilibrium temperatures clouds seem to dominate the transmission spectrum of exoplanets atmospheres, but no trends allowing the classification of these objects have yet emerged. Recently, Kepler observations of the light reflected by hot Jupiters show that an inhomogeneous, asymmetric and time-dependent cloud coverage is present in these planets. Interestingly, this asymmetry depends on the equilibrium temperature of the planet.
Using state-of-the-art three dimensional models of hot Jupiters atmospheres, I will show that longitudinal and latitudinal asymmetry in the cloud coverage is expected for these hot planets. The presence of such an inhomogeneous cloud coverage can bias the retrieved abundances from transmission and secondary eclipse spectra and even lead to erroneous molecular detections. Thermal phase curves are also affected, and our understanding of heat transport by the atmosphere cannot be complete without taking clouds into account. The longitudinal cloud asymmetry being a strong function of the condensation temperature of the cloud species, it is a telltale of the cloud composition. Observations and models converge towards a similar conclusion: an L/T-like transition is expected for hot Jupiters, with silicate clouds disappearing from the cooler planets and being replaced by manganese sulfide clouds. Local contact: P. O. Lagage; organization: P. O. Lagage |
Tuesday February 7 | Vacations / Vacances |
Tuesday February 21 10:00 | Francesco Pannarale (webpage) (Cardiff University)
Searching for Gravitational Waves Associated with Gamma-Ray Bursts in the Advanced Detector Era
Francesco Pannarale is co-chair of the LIGO-Virgo data analysis group for the follow-up of gamma-ray burst events and the recipient of the 2016 Special Breakthrough Prize in Fundamental Physics for contributing to the direct detection of gravitational waves. [click here for abstract] Gamma-ray bursts are the most luminous electromagnetic events in the universe. They fall into two, broad categories: long-duration (more than 2 s) bursts, which are powered by the core collapse of rapidly rotating massive stars, and short-duration (less than 2 s) bursts, for which binary neutron star and neutron star-black hole mergers are the leading progenitor candidates. In both scenarios, gravitational waves are expected to accompany the gamma-ray burst, making these transient phenomena promising events for gravitational-wave follow-up. In this talk, I review the status of targeted searches for gravitational waves in association with gamma-ray bursts and discuss the prospects of joint electromagnetic and gravitation-wave observations. I also present the results of these searches obtained during the first Advanced LIGO observing run, which was carried out between September 2015 and January 2016. Local contact: G. Migliori; organization: G. Migliori |
Tuesday March 7 10:00 | Vibor Jelic (Institut Ruder Boskovic ; Croatia)
Mysterious structures in our Galaxy obscuring the view towards the first stars in the Universe
Vibor Jelic is a research associate at Ruder Boskovic Institute in Croatia. He works on Faraday tomography of the local interstellar medium and the foreground studies in the cosmological 21cm experiments. He is actively involved in the LOFAR and the SKA projects. In 2013 he got a VENI grant from Netherlands Organisation for Scientific Research to explore the foreground emission below 250 MHz using a novel radio telescope LOFAR. [click here for abstract] With the novel world-leading radio telescope LOFAR (the Low Frequency Array), astronomers are expected to detect the cosmological radiation emitted billions of years ago, from the time of the first ‘stars’. However, detection of this weak emission is difficult. Synchrotron emission from our own Galaxy intervenes, like mist on an autumn morning. To clear the view towards the early childhood of the Universe, we need to study the emission from our Galaxy in great detail. During my talk I will give an overview of the LOFAR-EoR key science project, its challenges and present its most recent results. A special focus will be given to the rich morphological features discovered with the LOFAR in several fields at high Galactic latitudes, associated with small column densities of the interstellar medium located somewhere within the Local Bubble. At the end I will discuss their puzzling correlation with the Planck dust polarisation data and HI data. Local contact: A. Bracco; organization: V. Lebouteiller |
Thursday March 9 10:00 | Special seminar / séminaire exceptionnel Konstantinos Tassis (webpage) (Department of Physics, University of Crete)
PASIPHAE: Clearing the path to primordial B-modes through optopolarimetric magnetic tomography of the interstellar medium
Research interests: Star formation, physics of the interstellar medium, magnetohydrodynamics, cosmology
Management Panel Chair of the PASIPHAE Collaboration, http://pasiphae.science
Leader of the Interstellar Medium Group of the RoboPol Collaboration, http://robopol.org [click here for abstract] Polarized emission from cold Galactic dust is the most important and troublesome foreground for searches of an inflation-probing B-mode signal in the polarization of the cosmic microwave background (CMB). To get to the primordial B-modes, we need to subtract polarized emission of magnetized interstellar dust with high accuracy. A critical piece of this puzzle is the 3-d structure of the magnetic field threading dust clouds, which cannot be accessed through microwave observations alone. However, observations of a large number of stars at known distances in optical polarization, tracing the same CMB-obscuring dust, can map the magnetic field between them. The Polar Area Stellar Imaging in Polarization High Accuracy Experiment (PASIPHAE) will deliver such a map combining novel-technology wide-field-optimized optical polarimeters and an extraordinary commitment of observing time by the Skinakas observatory in Crete and the South African Astronomical Observatory. We will cover >9000 square degrees in the areas of the sky targeted by CMB experiments, measuring linear optical polarization at 0.2% accuracy of over 360 stars per square degree, a 1000-fold increase over the state of the art. Such a map would not only boost CMB polarization foreground removal, but it would also have a profound impact in a wide range of astrophysical research, including interstellar medium physics, high-energy astrophysics, and galactic evolution. Local contact: E. Ntormousi; organization: E. Ntormousi |
Tuesday March 21 10:00 | Special seminar / séminaire exceptionnel Arnaud Cassan (IAP)
Microlensing exoplanet search from space: results from Spitzer and K2 combined with ground-based surveys
[click here for abstract] The field of gravitational microlensing is booming, in particular due to the success of several space-based missions. I will review recent discoveries and developments in exoplanet search through gravitational microlensing, with a special focus on statistics of exoplanets, brown dwarfs and free-floating planets, and the Spitzer and Kepler/K2 follow-up of microlensing events using space-based parallax. I will outline the prospects of future techniques and instruments, such as the observations of microlensing events through interferometry and the promise of the WFIRST mission for microlensing. Local contact: S. Fromang; organization: K. Augustson |
Tuesday April 4 | Vacations / Vacances |
Tuesday April 18 10:00 | Francoise Combes (webpage) (Observatoire de Paris)
Star formation quenching: effect of AGN feedback and environment
[click here for abstract] Observations reveal that star formation is progressively quenched in more massive galaxies and in denser environments. What are the main physical mechanisms able to moderate and stop star formation?
An obvious one is the energetic feedback from AGN, where recently massive molecular outflows have been observed. Observational evidence will be shown with ALMA and NOEMA results. The mass outflow rate is estimated
between 1-5 times the star formation rate. When driven by AGN, these outflows are therefore a clear way to moderate or suppress star formation. However, AGN feedback can be also positive, and evidence will be presented.
Group and cluster environment can perturb considerably galaxies, quench their star formation, and transform their morphology in very short time-scales. I will present evidence of gas removal, where not only the external atomic gas is involved, but also inner molecular gas. Star formation still occurs in the tails, however with a much lower efficiency. The survival of dense clouds in harsh environments will be discussed. Local contact: F. Bournaud; organization: G. Migliori |
Tuesday May 2 10:00 | Georges Meynet (Université de Genève)
The massive stars along the cosmic history: from the first stars to the solar system formation.
[click here for abstract] In a first part of the seminar I shall discuss how from the observed surface abundances of extremely iron-poor stars, it is possible to deduce interesting properties of the first massive star generations in the Universe. These very iron-poor low mass (and therefore long-lived) stars are made of material made of a mixture of interstellar medium and of ejecta by a few, may be only one star. The very low iron content implies that not many generations of stars could enrich the pocket from which these iron-poor stars formed and thus favor short lifetimes stars as massive ones. The massive star(s) responsible for the main abundance properties of these very iron-poor stars are called the source star(s). First, based on nucleosynthetic arguments, we will deduce that necessarily some mixing processes occurred in the source stars and that only its outer layers have been ejected. Second we shall show how rotation might provide both the driving for the mixing and for the envelope ejection. Third, we shall discuss other consequences of these models for the production of nitrogen, carbon isotopes and s-process elements in the early Universe.
In a second part, if time permits, we would like to discuss the origin of some short lived radionuclides that were present, still non-decayed, in the cloud that gave birth to the solar system and were incorporated in some meteorites. We will see that the analysis of tiny amounts of meteoritic material can provide wonderful constraints on the near stellar environment of the solar system 4.56 Gyr ago. In that context we shall discuss the importance of mass loss by stellar winds that seems to be a key ingredient to explain the observed amounts of 26Al and 60Fe. Local contact: S. Mathis; organization: K. Augustson |
Thursday May 11 11:00 | Special seminar / séminaire exceptionnel Diego Blas (CERN)
Large scale structure in the mildly non-linear regime: analytical approaches
Diego Blas is staff scientist at CERN, Geneva. His main fields are gravitation and theoretical cosmology. He has been leading the studies on theoretical and phenomenological aspects of theories of quantum gravity with a preferred frame. In cosmology, he has developed new analytical tools to understand the formation of structure at large scales. He is a member of Spanish Society of Relativity and FQXi foundation. [click here for abstract] Structure formation is very sensitive to the primordial conditions and dynamical properties of the Universe. In fact, it is a promising probe of dark energy, dark matter properties, primordial non-gaussianity or neutrino masses. A major difficulty to harvest these results is that a significant fraction of the information lies at non-linear scales. It is thus essential (in particular to extract new physics) to develop efficient tools to study large scale structure beyond linear theory. In this talk I will describe the methods based on perturbation theory of a fluid-like medium, emphasising the new developments. The latter are particularly relevant to understand the evolution of the BAO and to parameterise the influence of small scales on mildly non-linear scales Local contact: V. Pettorino; organization: V. Lebouteiller |
Tuesday May 16 10:00 | Thorsten Naab (webpage) (Max-Planck-Institute for Astrophysics, Garching)
Physical processes setting the multiphase structure of the interstellar medium
Likes research on galactic dynamics, galaxy formation and insterstellar medium physics - interested in theoretical aspects of observational programs like ATLAS3D, PHIBBS, KMOS3D [click here for abstract] The interstellar medium (ISM) of galaxies drives galaxy evolution. However, its multi-phase structure is typically unresolved in cosmological galaxy formation simulations. I present recent progress on high-resolution numerical simulations (the SILCC project) investigating the differential impact of major physical processes setting the chemical and thermal multi-phase structure of the ISM including OB stellar winds, radiation and supernova explosions. We find evidence that stellar winds and radiation from massive stars primarily regulate star formation, while supernova explosions set the properties of the outflow driving hot gas. I also discuss the potential impact of non-thermal ISM components - magnetic fields and cosmic rays - on galactic outflows. With these simulations we also make first attempts towards more accurate predictions of important emission lines which are a major observables for galaxy formations studies at all cosmic epochs. Local contact: P. Hennebelle; organization: V. Lebouteiller |
Tuesday May 30 10:00 | Recent hiree seminar / séminaire arrivant récent Fabio Acero (DAp)
Recents news from supernova remnants in X- and gamma-rays
[click here for abstract] Supernova remnants 101:
The large amount of energy released in the supernova explosion leads to the creation of a fast shock wave which is an important source of kinetic and thermal energy in the interstellar medium. This shock wave is also believed to accelerate the bulk of Galactic cosmic rays.
As I believe that there has not been a general Supernova remnant (SNR) seminar in a long time, I will take this opportunity to make a short and biased introduction to SNRs, present the current scientific questions, and what we’ve learned from high-energy observations in the recent years.
In particular, I will focus on our recent work on the source RX J1713.7−3946, an excellent target to investigate particle acceleration in SNRs since it is one of the brightest sources of the TeV sky and exhibits strong synchrotron emission in X-rays. I will conclude by discussing SNRs from a population point of view in gamma-rays with the Fermi-LAT SNR catalog in the context of time dependent evolution models. Local contact: [-]; organization: V. Lebouteiller |
Tuesday June 13 10:00 | Enrico Corsaro (webpage) (INAF Catania Astrophysical Observatory)
Spin alignment of stars in old open clusters
Current position: Marie Sklodowska-Curie Fellow AstroFIt2 at INAF - Astrophysical Observatory of Catania, Sicily, Italy (prestigious fellowship obtained from a COFUND program between INAF and EU H2020 in 2016)
Achievements: main developer of DIAMONDS, Bayesian fitting tool widely recognized in the asteroseismic community for performing detailed asteroseismic analysis on oscillating stars; the research presented in the seminar was published in Nature Astronomy in March (+ journal cover for April issue) and has been conducted for most at CEA, in collaboration with the proto-cluster simulations group (P. Hennebelle and Y.-N. Lee) and with the asteroseismology group (R.A. Garcia, S. Mathis and P. Beck). [click here for abstract] Stars originate by the gravitational collapse of a turbulent molecular cloud of a diffuse medium, and are often observed to form clusters. Stellar clusters therefore play an important role in our understanding of star formation and of the dynamical processes at play. However, investigating the star formation is difficult because its physics is complex to be properly modeled, and because star forming regions are obscured by dust, which severely limits observations to infrared and radio bands only. As a consequence hierarchical-step approaches to decompose the problem into different stages are required, as well as reliable assumptions on the initial conditions in the clouds.
In this seminar I will report for the first time on the use of asteroseismology, namely the study of stellar oscillations, to put strong constraints on the early formation stages of open clusters, up to more than 8 billion years old. I will introduce you to asteroseismology, and then describe the analysis performed on a sample of 50 red giant stars in the old open clusters NGC 6791 and NGC 6819 observed by NASA Kepler, for which nearly 4000 oscillation modes have been fully characterized. I will therefore present the important discovery made about the rotation history of these clusters and how 3D hydrodynamical simulations for stellar cluster formation can be used to constrain the physical processes of turbulence and rotation that are in action during the proto-cluster formation. The results and implications of this work will be relevant for different fields in astrophysics, including planetary formation and galaxy formation, structure, and evolution. Local contact: R. Garcia; organization: K. Augustsson |
Tuesday June 27 10:00 | Cancelled / séminaire annulé Nanda Rea (Institute of Space Sciences (IEEC–CSIC), Barcelona, Spain)
Magnetic explosions in different neutron star classes
Local contact: G. Migliori; organization: G. Migliori |
Tuesday July 11 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Ivan Delvecchio (University of Zagreb)
The deepest radio view on AGN evolution in COSMOS
Local contact: E. Daddi; organization: E. Daddi |
SUMMER BREAK | |
Tuesday September 5 10:00 | Cancelled / séminaire annulé |
Tuesday September 19 10:00 | Anthony Jones (IAS)
Interstellar Dust Chemistry and Catalysis
[click here for abstract] In this talk I will focus on three aspects of interstellar dust that have a direct bearing on its chemistry and its effects on interstellar chemistry. These are:
- the nano-particle-driven catalytic formation of the key interstellar species H2 and OH, - the relationship between dust and the diffuse interstellar bands (DIBs) and - the nature and evolution of core/mantle grains in the interstellar medium. I will introduce these three topics and discuss what I would consider to be the fundamental links between them within the framework the recent interstellar dust model THEMIS (The Heterogeneous dust Evolution Model for Interstellar Solids; Jones et al. 2013, Köhler et al. 2014, 2015). In essence, it is my view that we can no longer think of dust as only providing a passive surface for the hit-stick-react-unstick formation of radicals and simple molecules such as molecular hydrogen. Instead we should consider the dust itself as a chemically-active source. As proposed within the THEMIS framework, dust is likely undergoing continuous evolution as it responds to its local environment, with the nature of the outer mantle layers playing a key role in that evolution (e.g., Jones et al. 2016, Ysard et al. 2016). This talk takes these ideas further and explores the consequences of an active evolution of dust within the ISM and its effects on the chemistry of the ISM. All of the ideas presented within this talk are published in a series of paper in Royal Society Open Science (Jones 2016a,b,c). Local contact: F. Galliano; organization: K. Augustson |
Tuesday October 3 10:00 | John M. Cannon (Macalester College, USA)
The Faint End of the Extragalactic HI Mass Function
[click here for abstract] Low-mass galaxies are the most numerous type of extragalactic system at all epochs of the universe. The population of low-mass galaxies in the local volume allows unique astrophysical and cosmological perspectives that are unavailable in more distant or more massive systems. The ALFALFA blind extragalactic HI survey has cataloged tens of thousands of gas-rich galaxies in the local universe and has populated the faint end of the HI mass function with statistical confidence for the first time. In this talk I will present results from comprehensive follow-up observing campaigns designed to study the low-redshift, low-mass, gas-rich population discovered by ALFALFA. The centerpiece of this effort is the Survey of HI in Extremely Low-mass Dwarfs (SHIELD), an ongoing multi-wavelength investigation of the properties of 82 extremely low-mass galaxies selected from the complete ALFALFA catalog. I will also discuss results from parallel ongoing observing programs that explore more exotic low-mass objects, including "ultra compact high velocity clouds" (HI clouds with structural parameters that match those of gas-bearing "mini-halos" if located within ~1 Mpc), candidate "dark galaxies" (systems with extreme hydrogen mass to stellar light ratios), and targeted studies of individual sources of interest (including two of the most metal-poor galaxies known in the universe). Taken as a whole, these observing programs are furthering our understanding of the continuum of galaxy properties in the low-mass regime. Local contact: V. Lebouteiller, F. Galliano; organization: G. Migliori |
Tuesday October 17 10:00 | Marta Volonteri (webpage) (IAP)
Growing black holes in growing galaxies
I work on cosmological aspects of the assembly of million solar masses black holes in the center of galaxies, and their connection to the evolution of cosmic structures and the high redshift universe. I am the PI of the research project BLACK, the cosmic evolution of massive black holes, funded by the European Research Council. [click here for abstract] Massive black holes, weighing millions to billions of solar masses, inhabit the centers of today's galaxies. Black hole masses typically scale with properties of their hosts, such as bulge mass and velocity dispersion. The progenitors of these black holes powered luminous quasars within the first billion years of the Universe. The first massive black holes must therefore have formed around the time the first stars and galaxies appeared, and then evolved along with their hosts for the past thirteen billion years. I will discuss some aspects of the cosmic evolution of massive black holes, from their formation to their growth and how different physical processes shape the relation between black holes and galaxies. Local contact: G. Migliori; organization: G. Migliori |
Wednesday October 18 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Daniel Gruen (SLAC/KIPAC/Stanford)
Weak gravitational lensing: cosmology results from the Dark Energy Survey
[click here for abstract] I will present cosmology constraints from a combined analysis of galaxy
clustering and weak gravitational lensing, using 1321 deg^2 of griz
imaging data from the first year of the Dark Energy Survey (DES Y1).
The analysis combines (i) the cosmic shear correlation function of 26
million source galaxies in four redshift bins, (ii) the galaxy angular
autocorrelation function of 650,000 luminous red galaxies in five
redshift bins, and (iii) the galaxy-shear cross-correlation of
luminous red galaxy positions and source galaxy shears. These three
measurements yield consistent cosmological results, and provide
constraints on the amplitude of density fluctuations (S_8 =
0.794+0.029-0.027) and dark energy equation of state (w =
-0.80+0.20-0.22) that are competitive and compatible with those from
Planck cosmic microwave background measurements. I will also provide
an outlook on upcoming weak lensing results from DES on clusters of
galaxies and density tomography, a newly developed higher-order
statistic. Local contact: M. Kilbinger; organization: M. Kilbinger |
Tuesday October 31 | Vacations / Vacances |
Tuesday November 14 10:00 | Carlo Manara (ESA)
Protoplanetary disk evolution: the key to planet formation
[click here for abstract] The evolution of protoplanetary disks is regulated by the interplay of various physical processes related to the interaction between the star and the disk, such as accretion of material onto the star and emission of material through winds. These processes are best studied spectroscopically. Instruments like the VLT/X-Shooter spectrograph allow us to observe simultaneously the signatures of the accretion process, such as the UV-excess and the emission lines, together with lines tracing winds and outflows, such as helium lines and forbidden lines. At the same time, such spectra allow us to robustly derive the physical parameters of the central objects, such as their temperature and their mass. When this information is combined with observations of disks at sub-mm wavelengths with ALMA it is then possible to quantitatively constrain disk evolution mechanisms. I will report on the dependence of the mass accretion rate with stellar mass and disk mass for the complete samples of low-mass objects in the Lupus and Chamaeleon star-forming regions, and discuss the theoretical framework we are working on to explain these observations. I will also present how we are using Gaia data to study young clusters, and how we are preparing to use future Gaia DR2 data to understand the effect of interactions between stars in the cluster on the evolution of disks. Local contact: A. Maury; organization: G. Migliori |
Tuesday November 28 10:00 | Joakim Rosdahl (Centre de Recherche Astrophysique de Lyon)
The Sphinx simulations: the first billion years and cosmic reionisation
Local contact: P. Hennebelle; organization: P. Hennebelle |
Tuesday December 12 10:00 | Recent hiree seminar / séminaire arrivant récent Julien Girard (DAp)
When sparsity meets radio interferometry in the SKA era
[click here for abstract] Radio astronomy is entering a new golden age with the emergence of continental-scale ground-based interferometers
such as LOFAR, MeerKAT and SKA. They provide a large field of view as well as high angular ("), spectral (Hz) and temporal
resolutions (microsecond) at huge sensitivity over a large frequency spectrum (from about 50 MHz to 10s of GHz). At the
same time, the recent mathematical framework of "Compressed Sensing" led to new signal processing algorithmic developments
that can be used for robust and sparse signal reconstructions. After introducing these two topics, I will present some developments done at their interface that are led by the team Cosmostat and LEPCHE in collaboration with SKA South Africa. Using the general « compressed sensing » framework combined with sparse representations and convex optimization, we developed two important applications for image reconstruction from interferometric data.
First, the improved performance of new instruments can be better exploited to study "slow" (more than 1min) and "fast" (less than 1min)
radio transients in the image plane. Unlike frame-by-frame detection, we extended the sparse reconstruction to the third
dimension by constraining the reconstruction in time, therefore increasing the detection and characterization of the
transient sources.
Second, LOFAR and SKA are essentially spectrometers which provide measurements in a very large number of frequency channels.
Each channel contains a mix of contributions from various astrophysical sources in the field of view. Based on a sparse source
separations method, it is possible to disentangle both spatially and spectrally the various contributions for proper spectral
imaging.
I will then discuss why more developments are required in this field to improve the scientific return of SKA-class instruments
with the advanced calibration of the deluge of data generated by these instruments. Local contact: G. Migliori; organization: G. Migliori |
2016 | |
Tuesday January 12 10:00 | Séminaire Présentation de Projets ERC // ERC Projects Seminar Anaëlle Maury, Jérôme Bobin (SAp)
The MagneticYSOs ERC project: characterizing the role of magnetic field
during the early stages of star/disk (Maury). LENA: non-linear signal processing for solving data challenging in astrophysics (Bobin)
Local contact: S. Juneau; organization: S. Juneau |
Tuesday January 26 10:00 | Joakim Rosdahl (Leiden, The Netherland)
RHD simulations of stellar radiation feedback in galaxies
Local contact: P.Hennebelle; organization: P.Hennebelle |
Tuesday February 9 10:00 | Benoît Cerutti (UJF/Observatoire de Grenoble)
Particle acceleration and radiation in pulsars: New insights from kinetic simulations
Local contact: T.Foglizzo, S.Fromang; organization: T.Foglizzo, S.Fromang |
Tuesday February 23 | Vacations / Vacances |
Friday March 4 14:00 | Special seminar / séminaire exceptionnel Nathan Jenkins (Authorea)
Data-driven, Interactive Scientific Articles in a Collaborative Environment with Authorea
Local contact: E. Ntormousi; organization: E. Ntormousi |
Tuesday March 8 10:00 | Matthieu Bethermin (ESO)
An ALMA view on the interstellar medium of lensed high-redshift dusty galaxies
Local contact: D.Elbaz, L.Ciesla; organization: D.Elbaz, L.Ciesla |
Tuesday March 22 10:00 | Selma de Mink (Amsterdam)
The Wonderful Lives of Massive Stars until their Final Explosions and Beyond
Local contact: T.Foglizzo; organization: S.Juneau |
Tuesday April 5 10:00 | Gregory Rudnick (Univ. of Kansas, USA)
The life cycle of galaxies in clusters over 10 billion years
Local contact: E. LeFloc'h; organization: E. LeFloc'h |
Tuesday April 19 | Vacations / Vacances |
Tuesday May 3 10:00 | no seminar |
Tuesday May 17 10:00 | Piero Madau (UCSC, US)
Cosmic Reionization after Planck: Progress and Challenges
Local contact: S. Juneau; organization: S. Juneau |
Tuesday May 31 10:00 | Karolina Mosiadz (Authorea)
Data-driven, Interactive Scientific Articles in a Collaborative Environment with Authorea
Local contact: E.Ntormousi; organization: E.Ntormousi |
Thursday June 9 10:00 | no seminar |
Tuesday June 14 10:00 | no seminar - SF2A |
Tuesday June 28 10:00 | Recent hiree seminar / séminaire arrivant récent Vianney Lebouteiller (SAp)
Gas heating in the neutral gas of extremely metal-poor galaxies
Local contact: S. Juneau; organization: S. Juneau |
SUMMER BREAK | |
Tuesday September 13 10:00 | Taddy Kodama (NAOJ)
Galaxies and clusters at the cosmic noon and beyond
Local contact: E.Daddi; organization: V. Lebouteiller |
Tuesday September 20 10:00 | Claudia Scarlata (Univ. of Minnesota)
Lyman alpha and Lyman continuum emission from galaxies
Local contact: E.Le Floc'h; organization: V. Lebouteiller |
Tuesday October 4 10:00 | Ian McCarthy (Liverpool, UK)
Interpreting the tension between the CMB and large-scale structure with hydrodynamical simulations
Local contact: A. Le Brun; organization: G. Migliori |
Tuesday October 11 10:00 | Special seminar / séminaire exceptionnel Felix Mirabel (SAp)
Formation of black holes in the dark
Local contact: V. Lebouteiller; organization: G. Migliori |
Tuesday October 18 10:00 | David Ehrenreich (Univ. of Geneva, Switzerland)
Evaporation of exoplanet atmospheres
Local contact: S. Fromang; organization: K. Augustson |
Tuesday November 1 | Holiday / Jour férié |
Tuesday November 15 10:00 | Hendrik Hildebrandt (Bonn Universit)
Weak Gravitational Lensing by Large-Scale Structure
Local contact: R. Van der Burg; organization: G. Migliori |
Tuesday November 29 10:00 | Joop Schaye (Leiden Observatory, The Netherlands)
Simulating the formation of galaxies
Local contact: A. Le Brun; organization: V. Lebouteiller |
Wednesday November 30 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Valérie Connaughton (NASA Marshall Space Flight Cente)
Fermi Gamma-ray Burst Monitor in the era of multi-messenger time-domain astronomy
Local contact: S. Schanne; organization: S. Schanne |
Tuesday December 13 10:00 | Chiara Ferrari (OCA Nic)
The Square Kilometre Array: science and technological challenge of the world largest radio telescope
Local contact: E. Daddi; organization: G. Migliori |
Wednesday December 14 10:00 Salle Cassini | Group seminar open to everybody / séminaire de groupe ouvert à tous Damiano Caprioli (University of Chicago)
New Insights on the origin of cosmic rays
Local contact: F. Acero; organization: F. Acero |
2015 | |
Tuesday January 13 10:00 | no seminar |
Tuesday January 27 10:00 | Arnaud Belloche (MPIfR Bonn, Germany)
Exploring Molecular Complexity with ALMA (EMoCA)
Local contact: A. Maury; organization: A. Maury |
Thursday February 5 14:30 Salle Cassini | Special seminar / séminaire exceptionnel Albrecht Poglitsch (MPE, Germany)
Lessons Learned (?) from the Herschel Mission
Local contact: S. Madden, L. Rodriguez; organization: S. Madden, L. Rodriguez |
Thursday February 12 11:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Peter Bierman (Univ. of Alabama, USA; Univ. of Bonn, Germany)
Cosmic backgrounds due to the formation of the first super-massive black holes
Local contact: F. Mirabel; organization: F. Mirabel |
Tuesday February 24 | Vacations / Vacances |
Tuesday March 10 10:00 | Eric Keto (CFA Harvard, USA, MPIA, Germany)
Hydrostatic Structure in the Interstellar Medium
Local contact: F. Motte; organization: F. Motte |
Tuesday March 24 10:00 | Bernard Bonin (CEA/DEN)
Un réacteur nucléaire pour le futur: le projet ASTRID
Local contact: G. A. Durand; organization: G. A. Durand |
Tuesday April 7 10:00 | Jayne Birkby (CFA-Harvard, USA)
Characterizing Exoplanet Atmospheres with High Resolution Spectroscopy
Local contact: R. Van Der Burg; organization: R. Van Der Burg |
Wednesday April 8 11:00 | Silvia Galli (KICP-U of Chicago, USA)
The latest results from the Planck satellite
Local contact: S. Juneau; organization: S. Juneau |
Tuesday April 21 10:00 | Cancelled / séminaire annulé Michaela Hirschmann (IAP)
The impact of stellar feedback on galaxy formation: insights from cosmological zoom simulations and galaxy formation models
Local contact: P.A. Duc, S. Juneau; organization: P.A. Duc, S. Juneau |
Tuesday May 5 10:00 | Francis Beaubois (Paris 6 UPMC, France)
De la theorie au modele : la constitution de l’astrophysique theorique dans les annees 1910-1930
Local contact: R. Lehoucq; organization: R. Lehoucq |
Tuesday May 19 10:00 | Cancelled / séminaire annulé Benoit Carry (IMCCE, France)
Solar system evolution from compositional mapping of the asteroid belt
Local contact: S. Juneau; organization: S. Juneau |
Tuesday June 2 10:00 | Adam Muzzin (Cambridge, UK)
How to Build a Big Galaxy
Local contact: R. Van Der Burg; organization: R. Van Der Burg |
Thursday June 4 11:00 | Special seminar / séminaire exceptionnel Luis Rodriguez (Univ. Autonoma de Mexico)
Massive Star Formation at the Puerto Varas Workshop
Local contact: F. Mirabel; organization: F. Mirabel |
Thursday June 18 11:00 | David Sanders (IfA Hawaii, USA)
A New View of the Galaxy "Main Sequence"
Local contact: F. Mirabel; organization: F. Mirabel |
Wednesday June 24 11:30 | Group seminar open to everybody / séminaire de groupe ouvert à tous Susmita Chakravorty (IPAG, Grenoble)
Magneto centrifugal winds from accretion discs around black hole binaries
Local contact: J. Rodriguez; organization: J. Rodriguez |
Thursday June 25 11:00 | Special seminar / séminaire exceptionnel Henk Hoekstra (Leiden Observatory, the Netherlands)
Weak lensing by large-scale structure as an accurate probe of cosmology and much more
Local contact: G. Pratt, S. Pires; organization: G. Pratt, S. Pires |
Tuesday June 30 10:00 | Nick Kaiser (IfA, Hawaii, USA)
On Novel Relativistic Effects in the Cosmological Distance-Redshift Relation
Local contact: H.Aussel; organization: H.Aussel |
Monday July 6 11:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Alexie Leauthaud (IPMU, Japan)
Evolving Galaxies in a Dark Universe
Local contact: D. Elbaz; organization: D. Elbaz |
Tuesday July 7 10:00 | Kevin Bundy (IPMU, Japan)
Why do galaxies die?
Local contact: D. Elbaz; organization: D. Elbaz |
SUMMER BREAK | |
Tuesday September 8 10:00 | Siraj S. Hasan (Indian Institute of Astrophysics, India)
A New Window on the Sun: The Indian National Large Solar Telescope
Local contact: S. Brun; organization: S. Brun |
Tuesday September 15 10:00 | Amy Yarleen Lien (Goddard Space Center, USA)
Gamma-ray Bursts from the Swift Burst Alert Telescope:
Probing Intrisic Distributions with Trigger Simulation
Local contact: A. Claret, S. Antier; organization: A. Claret, S. Antier |
Tuesday September 22 10:00 | Luca Ricci (CfA Harvard, USA)
Investigating the early formation and evolution of planetary systems
with sub-mm interferometers
Local contact: A. Maury; organization: A. Maury |
Tuesday October 6 10:00 | no seminar |
Thursday October 8 10:00 | Tsuyoshi Inoue (National Astronomical Observatory of Japan, Japan)
Dynamical Evolution of the Interstellar Medium Triggered by Shock Wave
Local contact: P. Hennebelle; organization: P. Hennebelle |
Tuesday October 20 10:00 | Roland Bacon (Lyon)
Beyond Hubble: MUSE offers a new view of the high redshift universe
Local contact: C.Cesarsky; organization: C.Cesarsky |
Tuesday November 3 10:00 | Eduard Vorobiev (Univ. of Vienna)
Formation of giant planets and brown dwarfs via disk fragmentation
Local contact: P. Hennebelle; organization: P. Hennebelle |
Tuesday November 17 10:00 | Michaela Hirschmann (IAP)
The impact of energetic phenomena on the evolution of galaxies and their black holes
Local contact: P.A. Duc, S.Juneau; organization: P.A. Duc, S.Juneau |
Monday November 30 11:00 | Gary Ferland (Univ. of Kentucky Lexington, USA)
Powering the optical filaments in cool core clusters of galaxies
Local contact: S. Juneau; organization: S. Juneau |
Monday December 7 11:00 | Special seminar / séminaire exceptionnel Takeru K. Suzuki (Univ. of Nagoya, Japan)
Winds from young suns and protoplanetary disks
Local contact: S. Brun; organization: S. Brun |
Friday December 11 11:00 | Rogier Windhorst (Arizona State Univ, USA)
How will the James Webb Space Telescope measure First Light, Reionization, and Galaxy Assembly: The New Frontier after Hubble
Local contact: C.Cesarsky; organization: C.Cesarsky |
2014 | |
Tuesday January 14 10:00 | Pierre Ferruit (ESA)
The James Webb Space Telescope and its instrument suite
Local contact: S. Juneau; organization: S. Juneau |
Tuesday January 28 10:00 | Jared Gabor (SAp)
Modelling galaxy evolution in a cosmological context
Local contact: S. Juneau; organization: S. Juneau |
Tuesday February 11 10:00 | Martin Kilbinger (SAp)
Exploring the dark universe with weak gravitational lensing
Local contact: S. Pires; organization: S. Pires |
Tuesday February 25 10:00 | Brent Tully (IfA, Honolulu, USA)
Cosmicflows-2
Local contact: S. Juneau; organization: S. Juneau |
Tuesday March 11 10:00 | Enrico Barausse (IAP)
Compact objects as probes of astrophysics, gravity, and fundamental physics
Local contact: S. Juneau; organization: S. Juneau |
Tuesday March 18 10:00 | Daniel Schaerer (Observatoire de Genève)
Physical Properties of distant star forming galaxies
Local contact: D. Elbaz; organization: D. Elbaz |
Tuesday March 25 10:00 | Tommaso Giannantonio (LMU, Munich)
Testing dark energy and inflation with galaxy surveys and their external correlations
Local contact: M. Kilbinger; organization: M. Kilbinger |
Tuesday April 8 10:00 | no seminar |
Thursday April 17 10:00 | Martin Stringer (IAP)
Galaxy properties as a fingerprint of cosmology and fundamental physics
Local contact: S. Geen; organization: S. Geen |
Tuesday April 22 10:00 | S. Mohanty (Imperial College London)
Angular Momentum Evolution in Low-Mass Stars : A Fresh Look
Local contact: E. Ntormousi; organization: E. Ntormousi |
Tuesday May 6 10:00 | Coralie Neiner (Obs. de Paris Meudon, France)
Magnetic fields in massive stars
Local contact: S. Mathis; organization: S. Mathis |
Thursday May 15 10:00 | Kumiko Kotera (IAP)
Pulsars: a promising source for high and ultrahigh energy cosmic rays
Local contact: S. Juneau; organization: S. Juneau |
Tuesday May 20 10:00 | Sara Ellison (UVic, Canada)
Galaxy mergers in the nearby universe
Local contact: S. Juneau; organization: S. Juneau |
Wednesday May 21 11:00 | Guillaume Loisel (Sandia National Laboratories, NM, USA)
Progress and Status of ZAPP: the Z Astrophysical Plasma Properties collaboration
Local contact: S.Turck-Chieze; organization: S.Turck-Chieze |
Tuesday May 27 14:30 | Yasuo Fukui (Nagoya University, Japan)
Optically thick HI in the local interstellar medium: An alternative to "dark gas"
Local contact: S. Madden; organization: S. Madden |
Tuesday June 3 10:00 | no seminar - SF2A |
Thursday June 19 11:00 | Joanne Dawson (CSIRO, Australia)
From Supershells to Stars to Hidden Molecular Clouds: Charting the Life Story of Gas in Galaxies
Local contact: E. ; organization: E. |
Tuesday July 1 10:00 | Guillermo Barro (UC Santa Cruz, USA)
Live fast, die... small: The fall of the first massive galaxies
Local contact: D. Elbaz; organization: D. Elbaz |
Friday July 4 11:00 | George Ricker (MIT Kavli Institute, USA)
TESS: The Transiting Exoplanet Survey Satellite
Local contact: R. Garcia; organization: R. Garcia |
Tuesday July 15 10:00 | Marc Pinsonneault (Ohio State University, USA)
The APOGEE-KEPLER Survey: A new window on Stellar Populations and Stellar Physics
Local contact: R. Garcia; organization: R. Garcia |
SUMMER BREAK | |
Tuesday September 9 10:00 | Hitoshi Negoro (Nihon University, Japan)
Monitor of All-sky X-ray Image onboard the International Space Station:
Observation and Results
Local contact: J. Rodriguez; organization: J. Rodriguez |
Monday September 15 11:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Subhabrata Majumdar (TIFR, India)
Cluster Core Energetics
Local contact: A. Roy; organization: A. Roy |
Friday September 19 11:00 | Special seminar / séminaire exceptionnel Eli Dwek (NASA Goddard, USA)
Dust destruction and formation rates in the Magellanic Clouds,
and the evolution of dust in the very high redshift Universe
Local contact: F. Galliano; organization: F. Galliano |
Tuesday September 23 10:00 | Gilles Chabrier (ENS Lyon)
Structure and evolution of giant planets: from physics to astrophysics
Local contact: S. Fromang; organization: S. Fromang |
Tuesday October 7 10:00 | David Alexander (Durham University, UK)
Active Galaxies in Cosmic X-ray Surveys: The Ecology of Distant AGNs
Local contact: D. Elbaz; organization: D. Elbaz |
Tuesday October 21 10:00 | G. Durand, S. Correia, M. Sauvage (DAp)
TALC: un projet de télescope spatial infrarouge lointain de 20m pour succéder à Herschel
Local contact: G. Durand; organization: G. Durand |
Tuesday November 4 10:00 | Vivienne Wild (St Andrews, UK)
Searching for the origins of galaxy bimodality
Local contact: S. Juneau; organization: S. Juneau |
Thursday November 20 11:00 | Ellen Zweibel (Wisconsin, USA)
The macrophysics and microphysics of cosmic rays
Local contact: S. Juneau; organization: S. Juneau |
Tuesday December 2 10:00 | Patrick Hennebelle (DAp)
Influence of stellar feedback processes at small and very small galactic scales
Local contact: S. Juneau; organization: S. Juneau |
Tuesday December 16 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Jérôme Guilet (MPA-Garching, Germany)
Magnetic field amplification in proto-neutron stars
Local contact: A. Maury, T. Foglizzo; organization: A. Maury, T. Foglizzo |
Thursday December 18 11:00 | Special seminar / séminaire exceptionnel David Valls Gabaud (LERMA, Obs. de Paris)
The MESSIER satellite: Unveiling galaxy formation
Local contact: P.A. Duc ; organization: P.A. Duc |
2013 | |
Thursday January 10 11:00 | R. Kuiper (Tubigen University)
Radiation Pressure in Massive Star Formation
Local contact: [-]; organization: [-] |
Thursday January 17 10:00 | Philippe André (SAp)
From filamentary networks to dense cores in molecular clouds: Toward a unified picture for star formation ?
Local contact: [-]; organization: [-] |
Thursday January 24 10:00 | no seminar - AERES |
Thursday January 31 11:00 | C. Charbonnel (Observatoire de Genève)
Multiple stellar populations in globular and massive star clusters: Formation, evolution, dynamics
Local contact: [-]; organization: [-] |
Friday February 8 11:00 | [TBA] |
Thursday February 14 11:00 | C. Michaut (IPGP, Paris)
Evolution thermique et magmatisme des planetes telluriques
Local contact: [-]; organization: [-] |
Thursday February 21 14:00 | Stéphanie Juneau (SAp)
Hidden supermassive black holes in star-forming galaxies
Local contact: [-]; organization: [-] |
Tuesday February 26 14:00 | E. Spiegel (Columbia University, NY)
Order amidst chaos in the Sun
Local contact: [-]; organization: [-] |
Friday March 22 11:00 | S. Markoff (Amsterdam University)
Our Galactic supermassive black hole Sgr A*: the ideal testbed for theories of accretion and black hole life cycles
Local contact: [-]; organization: [-] |
Thursday March 28 11:00 | N. Lagarde (Array)
Spectroscopic and asteroseismic diagnostics on mixing processes inside red giant stars
[click here for abstract] Birmingham University Local contact: [-]; organization: [-] |
Thursday April 11 11:00 | J. Leconte (Laboratoire de Météorologie Dynamique)
A new vision of giant planet interiors: double diffusive "layered" convection as the origin of Saturn's luminosity anomaly
Local contact: [-]; organization: [-] |
Thursday April 25 11:00 | D. Kunth (IAP)
L'émission Lyman alpha dans l'Univers
Local contact: V. Lebouteiller; organization: V. Lebouteiller |
Thursday May 16 11:00 | P. Lesaffre (LERMA, Obs de Paris)
Turbulence dissipation and the chemistry of the diffuse ISM
Local contact: S. Fromang; organization: S. Fromang |
Thursday May 23 11:00 | D. Stark (University of Arizona)
Early Star Forming Galaxies and Cosmic Reionization
Local contact: S. Juneau; organization: S. Juneau |
Tuesday June 4 10:30 | Special seminar / séminaire exceptionnel René Rupert (Consultant pour le compte d'institutions diverses en France, Suisse, Autriche)
Intégration du facteur humain dans la conduite des projets
Local contact: M. Talvard; organization: M. Talvard |
Thursday June 6 10:00 | Roberto Mignani (University College London)
The multi-facet view of Neutron stars
Local contact: F. Mirabel; organization: F. Mirabel |
Wednesday June 19 11:00 | Tony Bell (University of Oxford)
Particle acceleration by shocks
Local contact: I. Grenier; organization: I. Grenier |
Thursday July 4 11:00 | Cancelled / séminaire annulé S. Mohanty (Imperial College London)
Dead, Undead and Zombie Zones in Protostellar Disks: Can the MRI Survive?
Local contact: E.Ntormousi; organization: E.Ntormousi |
SUMMER BREAK | |
Tuesday September 17 10:00 | Lisa Kewley (Australian National University)
The Cosmic Spectral Evolution of Starburst and AGN
Local contact: S. Juneau; organization: S. Juneau |
Tuesday September 24 10:00 | Chris Conselice (University of Nottingham)
Galaxy Assembly as a New Probe of Cosmology
Local contact: S. Juneau; organization: S. Juneau |
Tuesday October 8 10:00 | no seminar |
Monday October 21 15:00 | Special seminar / séminaire exceptionnel Pisin Chen (Leung Center for Cosmology and Particle Astrophysics, Taiwan)
Recent Progress in Particle Astrophysics and Cosmology
Local contact: C. Cesarsky; organization: C. Cesarsky |
Tuesday October 22 10:00 | Group seminar open to everybody / séminaire de groupe ouvert à tous Takashi Onaka (Tokyo University)
AKARI infrared satellite and its Large Magellanic Survey and beyond
Local contact: R. Wu; organization: R. Wu |
Tuesday November 5 10:00 | Pieter DeGroote (University of Leuven - KU Leuven)
Asteroseismology of massive stars
Local contact: S. Mathis; organization: S. Mathis |
Tuesday November 19 10:00 | Gabriel Tobie (Université de Nantes)
Saturn's moon Enceladus: Origin of its surprising activity
Local contact: S. Rodriguez; organization: S. Rodriguez |
Wednesday November 27 11:00 | Sean Carroll (Caltech)
The Origin of the Universe and the Arrow of Time
Local contact: S. Juneau; organization: S. Juneau |
Tuesday December 3 10:00 | Hervé Dole (IAS, Orsay)
Planck and the Large Scale Structures
Local contact: S. Corbel; organization: S. Corbel |
Tuesday December 17 10:00 | Clare Dobbs (Exceter)
The evolution of Giant Molecular Clouds
Local contact: F. Bournaud; organization: F. Bournaud |
Wednesday December 18 10:00 | Thomas Lepeltier (Oxford)
La cosmologie est-elle scientifique? Histoire d'une interrogation
Local contact: S. Chaty; organization: S. Chaty |
Tuesday November 19 10:00 | Postdoc seminar / séminaire postdoc Jose Ignacio "Nacho" ANEZ LOPEZ (LFEMI)
Signatures of magnetic braking in Class 0 protostars ? Exploring the gas kinematics in magnetized models of low-mass star formation
[click here for abstract] The role of magnetic braking in regulating gravitational collapse and circumstellar disk during the main accretion phase, is an open question. While only indirect evidence was found from observational work, such as compact disk sizes and the launching of high-velocity collimated jets, we aim at more direct tests of the magnetic braking in observations. The study of polarized dust emission as a tracer of the magnetic field and molecular line emission as a tracer of gas kinematics in young protostars can provide valuable information for understanding how the presence of the magnetic field affects the accretion process.
In the present work, we have used both non-ideal MHD models and synthetic observations from the radiative transfer of protostellar formation to put constraints on the magnetically-regulated disk formation scenario. We use our model synthetic observations to identify possible direct signatures of the magnetic braking from the maps of the molecular gas emission. By comparing the specific angular momentum of two similar models that differ in magnetic flux, we see that the more magnetized model shows a higher angular momentum redistribution above 1000 au. In addition, we have tested the methods typically used to infer the specific angular momentum from an observational point of view. We have found possible observational evidence of magnetic braking in the kinematics of the C18O(2-1) molecule, such as a flattening of the radial profile of specific angular momentum for radii smaller than 1000 au for the more magnetized model similar to the characteristics found in observational work. On the other hand, in this study we show that the maximum velocity computed in the equatorial plane, which is traditionally used as an approximation of the rotational velocity, may overestimate the rotational velocity, probably due to contamination from radial motions. Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday November 26 | Special event / Événement spécial Visite de l'HCERES (AIM) / no seminar |
Tuesday December 3 10:00 | Stefano CAMERA (University of Turin)
Synergic cosmology across the spectrum
[click here for abstract] In my talk, I shall review the main research projects I'm involved in, which all revolve around the added value of cross-correlations between various cosmological observables, as well as among cosmological and astrophysical observables, to shed new light onto pressing open questions in cosmology. In particular, I shall touch upon the possibility of detecting relativistic effects on cosmological scales - which will allow us to deepen our understanding of dark energy and modified gravity -, novel approaches to probe primordial non-Gaussianity, and the use of cosmological data to filter out astrophysical processes in studies of indirect detection of particle dark matter signatures. All this in the view of the new generation of cosmological experiments across the electromagnetic spectrum, like the SKA Observatory in the radio band, or the Euclid satellite at optical/near-infrared wavelengths. Local contact: Martin KILBINGER; organization: Fabian HERVAS-PETERS |
Tuesday December 10 | Special event / Événement spécial Visite de l'HCERES (Irfu) / no seminar |
Tuesday December 17 10:00 | Jean BALLET, Anne DECOURCHELLE, Gabriel PRATT et al. (LEPCHE)
Les 25 ans d'XMM
[click here for abstract] Lancé le 10 décembre 1999, le satellite XMM-Newton d'observation en rayons X fêtera ses 25 ans d'opération et d'exploitation scientifique, et une moisson de résultats scientifiques dans de nombreux domaines. Nous vous invitons mardi 17 septembre 2024 à un séminaire d'anniversaire de la mission XMM-Newton, pierre angulaire du programme Horizon 2000 de l'Agence Spatiale Européenne. Nous retracerons à plusieurs voix l'implication du DAp-AIM dans la réalisation et l'exploitation des données de XMM-Newton, et vous présenterons une sélection de résultats scientifiques marquants. Local contact: Anne DECOURCHELLE; organization: Pierre-Antoine FRUGIER |
2025 | |
Tuesday January 7 10:00 | Postdoc seminar / séminaire postdoc Emma AYÇOBERRY (LCS)
Thermal Sunyaev-Zel’dovich power spectrum: analytical model and measurement in simulations
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday January 14 10:00 | Postdoc seminar / séminaire postdoc Maximilien FRANCO (LCEG)
Characterization of the brightest galaxies during the Epoch of Reionization in COSMOS-Web
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday January 21 10:00 | Recent hiree seminar / séminaire arrivant récent Ugo LEBREUILLY (LMPA)
Gas and dust evolution during protoplanetary disk formation
Local contact: Ugo LEBREUILLY; organization: Frédéric GALLIANO |
Tuesday January 28 10:00 | Samuel LANDER (University of East Anglia)
The first five minutes in the life of a neutron star's magnetic field
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 4 10:00 | Postdoc seminar / séminaire postdoc Arthur LE SAUX (LDE3)
Unveiling stellar internal dynamics with hydrodynamical simulations
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 11 10:00 | Postdoc seminar / séminaire postdoc Roberta GIUFFRIDA (LEPCHE)
[TBA]
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday February 18 | Vacations / Vacances Vacances d'hiver |
Tuesday February 25 | Vacations / Vacances Vacances d'hiver |
Tuesday March 4 10:00 | Postdoc seminar / séminaire postdoc Joey MOMBARG (LDE3)
The next step in stellar evolution: towards multi-dimensional models
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday March 11 10:00 | Postdoc seminar / séminaire postdoc Cail DALEY (LCS)
CMB Lensing Measurements with Two Years of Data from the SPT-3G Survey
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday March 18 10:00 | [TBA] |
Tuesday March 25 10:00 | [TBA] |
Tuesday April 1 10:00 | Evan O'CONNOR (Stockholm University, Sweden)
Recent Advances in Core-Collapse Theory
Local contact: Thierry FOGLIZZO; organization: Frédéric GALLIANO |
Tuesday April 8 10:00 | LCS invitee (Array)
.
Local contact: [-]; organization: [-] |
Tuesday April 15 | Vacations / Vacances Vacances de printemps |
Tuesday April 22 | Vacations / Vacances Vacances de printemps |
Tuesday April 29 10:00 | [TBA] |
Tuesday May 6 10:00 | [TBA] |
Tuesday May 13 10:00 | [TBA] |
Tuesday May 20 10:00 | Natascha FORSTER SCHREIBER (Max-Planck-Institut für extraterrestrische Physik)
Star-Forming Galaxies at Cosmic Noon and Beyond
Local contact: Emanuele DADDI; organization: Frédéric GALLIANO |
Tuesday May 27 10:00 | [TBA] |
Tuesday June 3 10:00 | [TBA] |
Tuesday June 10 10:00 | [TBA] |
Tuesday June 17 10:00 | [TBA] |
Tuesday June 24 10:00 | [TBA] |
SUMMER BREAK |