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mai 2017
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David Elbaz (CEA-Saclay) — Do we really know how galaxies formed their stars through cosmic time ?

Vendredi 5 mai 11:00-12:00 - Amphi

Abstract : There is a growing opinion among astrophysicists that we now have a clear picture about how galaxies formed their stars through cosmic time. It is thought that numerical simulations reproduce the observed Universe well enough and that we have now entered the era of the last refinements that will only validate a list of common assumptions, providing more digits in quantitative numbers measuring star formation rates, efficiencies, gas fractions, black hole masses etc.
Paradoxically, there are at the same time open questions that regularly emerge in this picture : how can a large galactic disk form and then survive a large series of merger events ? why do galaxies become passive when the vast majority of baryons remain in the form of diffuse gas in a Universe dominated by dark matter ? Dense environments segregate galaxy morphologies and yet observational evidence for an impact of the environment on the rate of star formation within galaxies remain elusive. And if we were missing a major piece of the puzzle hidden behind the so called details ? Do black holes play a role in galaxies’ history or do they just follow in parallel, and does this role inhibit or activate star formation ? I will present recent published and unpublished results obtained with Herschel and ALMA that bring some new light in this picture with peculiar emphasis on-the existence of HST-dark galaxies that may represent the missing link to understand massive galaxy formation - the ALMA view on the so-called SFR M* main sequence of galaxies - evidence for a new population of starbursts hidden within this main sequence - evidence for a paradoxical universality of galaxy growth suggesting that stellar feedback may be more a self-regulating process in galaxies than a quenching mechanism - and counter-intuitive evidence for a positive feedback of galactic black holes.

Pierre-Olivier Lagage (CEA-Saclay) — Characterization of the atmosphere of exoplanets with the JWST

Vendredi 12 mai 11:00-12:00 - Amphi

Abstract : Next year (Oct 2018), the James Webb Space Telescope will be launched. With a collecting area of 25 m², this observatory is expected to have a huge impact on many fields of astrophysics. In this talk, after having reviewed the capabilities of the JWST, shared the latest news about its status, described the timeline for forthcoming calls for science observations, I will focus on one of the main themes of the JWST : exoplanets. I will illustrate the JWST potential in the field by describing the exoplanet observations to be done in the framework of Guaranteed Time Observations (GTO). The large Signal over Noise ratio and wavelength coverage that the JWST will bring, made us studying the precision of the atmospheric models used to interpret the observation. I will present the results from benchmarking three atmospheric models. I will also show that some simplifications made so far in the models used to retrieve atmospheric parameters from observations will no longer be valid.

NO Seminar — No seminar

Vendredi 19 mai 11:00-12:00 - Amphi

NO Seminar — No seminar

NO Seminar — No seminar

Vendredi 26 mai 11:00-12:00 - Amphi

NO Seminar — No seminar

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