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:
1. disentangle spatially resolved galaxy SEDs from dust contribution, free-free and synchrotron emission;
2. constrain the evolution of the dust-to-gas mass ratio within galaxies, which provides a direct link to the chemical evolution of galaxies and the reservoirs for dust production;
3. study the microscopic properties of dust, i.e. constraints on millimetric opacity;
4. study the sub-millimetre excess in galaxies, whose origin is still unknown.
These are some of the main objectives of the IMEGIN Large Program (Interpreting the Millimetre Emission of Galaxies with IRAM-NIKA2; PI S. Madden), targeting 22 nearby galaxies in the millimetre continuum regime with the NIKA2 camera. The millimetre data, combined with a suite of observations at other wavelengths, allow us to model the IR-to-radio SED and to put constraints on interstellar medium and dust grains properties of galaxies. We perform the galaxy SED analysis using the hierarchical bayesian fitting code HerBIE (Galliano et al. 2018), which includes the prescriptions from the dust evolution model THEMIS (Jones et al. 2017), anchored to the laboratory-measured properties of inter-stellar dust analogues.
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 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:
- Stephan Aune (CEA, SEDI) - Design and construction by CEA Paris-Saclay
- Jean-Charles Cuillandre (CEA, DAp) - Scientific operation at CFHT
- Pierre Astier (IN2P3, LPNHE) - Supernovae and the Dark Energy equation-of-state 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 | 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 | 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:
a) Explore and resolve heavily populated sky regions, in particular the Galactic Center to resolve the nature and environment of the central massive black hole, to decipher the nature of its emission, such as the emission associated with the dark matter, new types of sources, or currently unresolved population of point sources. The GC long-term observation with ~1 arcmin angular resolution could be crucial in disentangling new physics in unexplored energy range. The Carina OB1 and OB2 associations, home to the most massive and luminous stars in the Milky Way, and Cygnus region, are other crowded places where high angular resolution is needed to resolve sources.
b) Large FoV monitoring for transient events, detected with high sensitivity and accurate localization, performing multimessenger investigations to support GW and neutrino discoveries.
Also, GECCO’s observational capability to disentangle discrete sources from truly diffuse emission and high energy resolution will contribute to understanding the gamma-ray Galactic Center excess and the Fermi Bubbles, and to tracing low-energy cosmic rays and their propagation in the Galaxy. Nuclear and annihilation lines will be spatially and spectrally resolved from continuum emission and from sources, addressing the role of low-energy cosmic rays in star
formation and galaxy evolution, the origin of the 511 keV positron line, fundamental physics, and Galactic chemical evolution. Of special interest will be the exploration of sites of explosive element synthesis by conducting high-sensitivity measurements of nuclear lines from Type 1a supernovae and from other objects.
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:
1. disentangle spatially resolved galaxy SEDs from dust contribution, free-free and synchrotron emission;
2. constrain the evolution of the dust-to-gas mass ratio within galaxies, which provides a direct link to the chemical evolution of galaxies and the reservoirs for dust production;
3. study the microscopic properties of dust, i.e. constraints on millimetric opacity;
4. study the sub-millimetre excess in galaxies, whose origin is still unknown.
These are some of the main objectives of the IMEGIN Large Program (Interpreting the Millimetre Emission of Galaxies with IRAM-NIKA2; PI S. Madden), targeting 22 nearby galaxies in the millimetre continuum regime with the NIKA2 camera. The millimetre data, combined with a suite of observations at other wavelengths, allow us to model the IR-to-radio SED and to put constraints on interstellar medium and dust grains properties of galaxies. We perform the galaxy SED analysis using the hierarchical bayesian fitting code HerBIE (Galliano et al. 2018), which includes the prescriptions from the dust evolution model THEMIS (Jones et al. 2017), anchored to the laboratory-measured properties of inter-stellar dust analogues.
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 Rebeca BATALHA DE MELO (LEPCHE)
[TBA]
Local contact: Thierry FOGLIZZO, organization: Frédéric GALLIANO |
Tuesday November 14 | Special event / Événement spécial Local meeting |
Tuesday November 21 10:00 | Recent hiree seminar / séminaire arrivant récent Camila CORREA (LCEG)
[TBA]
Local contact: Frédéric BOURNAUD, organization: Carlos GÓMEZ GUIJARRO |
Tuesday November 28 10:00 | Elisa CHISARI (University of Oxford)
[TBA]
Local contact: Martin KILBINGER, organization: Fabian HERVAS PETERS |
Tuesday December 5 10:00 | Recent hiree seminar / séminaire arrivant récent Barbara PERRI (LDE3)
[TBA]
Local contact: Barbara PERRI, 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 |
Laboratoire AIM (Astrophysique, Instrumentation, Modélisation)
Français English |
Le Commissariat à l'énergie atomique et aux énergies alternatives
Français English |
Institut de Recherche sur les lois Fondamentales de l'Univers
Français English |