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: March 4, 2024)


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






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
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



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: Frédéric GALLIANO
Tuesday

April 2

10:00
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

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



Local contact: Jérôme BOBIN, organization: Fabian HERVAS PETERS
Tuesday

April 30

10:00
Postdoc seminar / séminaire postdoc
Dinil PALAKKATHARAPPIL
(LDE3)

Sismology in Stellar Clusters



Local contact: Thierry FOGLIZZO, organization: Frédéric GALLIANO
Tuesday

May 7

10:00
Thomas HENNING
(Max Planck Institute for Astronomy, Heidelberg)

Star and Planet Formation with JWST



Local contact: Frédéric GALLIANO, organization: Frédéric GALLIANO
Tuesday

May 14

10:00
Recent hiree seminar / séminaire arrivant récent
Damien TURPIN
(DAp)

Le ciel transitoire multi-messagers dans la perspective du lancement de SVOM



Local contact: Damien TURPIN, organization: Frédéric GALLIANO
Tuesday

May 21

10:00
Climate seminar / séminaire climat
Céline GUIVARCH
(CIRED / GIEC)

Le coût des politiques climatiques



Local contact: Nicolas CERARDI, organization: Nicolas CERARDI
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 m line of [NII] and 158 m 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)

Nanosatellites pour l’étude de l’albedo terrestre et du flux solaire



Local contact: Henri TRIOU, organization: Pierre-Antoine FRUGIER
Tuesday

June 18

10:00
[TBA]
Tuesday

June 25

10:00
[TBA]


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
[TBA]
Tuesday

October 15

10:00
[TBA]
Tuesday

October 22

Vacations / Vacances
Vacances de la Toussaint
Tuesday

October 29

Vacations / Vacances
Vacances de la Toussaint
Tuesday

November 5

10:00
[TBA]
Tuesday

November 12

10:00
[TBA]
Tuesday

November 19

10:00
[TBA]
Tuesday

November 26

10:00
[TBA]
Tuesday

December 3

10:00
[TBA]
Tuesday

December 10

10:00
[TBA]
Tuesday

December 17

10:00
[TBA]





Year-by-year program:

             







Seminars in other places:

IAS, IAP, IHES









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