CEA/DAp SEMINAR ORGANIZATION

The Astrophysics Seminars of the DAp (Département d'Astrophysique) are held at the Orme des Merisiers campus of the CEA Saclay. The schedule is posted on this website. Unless otherwise posted, the seminar takes place at 10am on Tuesdays in room Galilée (Building 713C).

Current seminar organization team: Frédéric GALLIANO, Pierre-Antoine FRUGIER, Carlos GOMEZ-GUIJARRO, Fabian HERVAS PETERS.

Main official page for advertising the program: http://irfu.cea.fr/dap/Phocea/Vie_des_labos/Seminaires/index.php?type=3






Past seminar and next ones (current date: June 18, 2024)


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








Year-by-year program:

             





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.

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; https://science.nasa.gov/astrophysics/programs/habitable-worlds-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
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. - Mais pourquoi est-il important pour nous d'étudier le bilan énergétique de la Terre ? - Que peuvent apporter les observations Uvsq-Sat ? - En ce qui concerne les phénomènes naturels et les activités humaines, quels sont les principaux impacts sur le bilan énergétique ? Autant de questions qui seront abordées en introduction de cette conférence. Les opérations en orbite et les résultats obtenus avec la mission Uvsq-Sat seront également présentés. L’intérêt d’utiliser des constellations de satellites sera aussi expliqué. De plus, cette conférence couvrira le développement et le lancement d'un autre satellite (avril 2023), Inspire-Sat, élaboré par le LATMOS. Enfin, nous mettrons en avant le développement du troisième satellite, dénommé Uvsq-Sat NG et qui doit être mis en orbite en février 2025.

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 3

10:00
[TBA]
Tuesday

September 10

10:00
[TBA]
Tuesday

September 17

10:00
[TBA]
Tuesday

September 24

10:00
[TBA]
Tuesday

October 1

10:00
[TBA]
Tuesday

October 8

10:00
Lorenzo DUCCI
(University of Tübingen)

X-ray binaries



Local contact: Diego GÖTZ, organization: Frédéric GALLIANO
Tuesday

October 15

10:00
Climate seminar / séminaire climat
Sophie SCHBATH
(INRAE)

Le développement durable au sein d'un laboratoire de recherche



Local contact: Jérôme GUILET & Roland LEHOUCQ, organization: Frédéric GALLIANO
Tuesday

October 22

Vacations / Vacances
Vacances de la Toussaint
Tuesday

October 29

Vacations / Vacances
Vacances de la Toussaint
Tuesday

November 5

10:00
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
[TBA]
Tuesday

November 19

10:00
[TBA]
Tuesday

November 26

Special event / Événement spécial
Visite de l'HCERES / no seminar
Tuesday

December 3

10:00
Anne DECOURCHELLE
(LEPCHE)

Les 25 ans d'XMM



Local contact: [-], organization: [-]
Tuesday

December 10

10:00
[TBA]
Tuesday

December 17

10:00
Anne DECOURCHELLE
(LEPCHE)

Les 25 ans d'XMM



Local contact: [-], organization: [-]





Year-by-year program:

             







Seminars in other places:

IAS, IAP, IHES









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