Hans Zinnecker : Airborne Infrared Observations with SOFIA @ Univers 21
Sep 26 @ 11 h 00 min – 12 h 00 min

SOFIA, short for Stratospheric Observatory for Infrared Astronomy,
is a 2.7m telescope flying on a Boeing 747SP at altitudes of 12-14km,
to detect and study mid- and far-infrared radiation that is blocked
by water vapor in the earth’s atmosphere and cannot reach the
ground. It is the successor to the Kuiper Airborne Observatory (1974-1995)
and currently the only access to and platform for astronomical observations
in the far-infrared (30-300 microns), except for balloon-borne telescopes.

Although a bilateral project (80:20)
between USA (NASA/USRA) and Germany (DLR/DSI), it is open for
proposals from the world-wide astronomical community at large.
It addresses many science questions that ESA’s successful but
now extinct Herschel Observatory has left unanswered and
offers observational opportunities similar to and beyond Herschel.
SOFIA also has many synergies with ALMA and APEX, as well as the IRAM
submm and radio telescopes.

In my presentation, I will describe a glimpse of SOFIA science
highlights and discoveries in its first few years of operation,
both in astrochemistry (light molecules) and in astrophysics
(dynamics of star formation). I will also touch upon the science
prospects of new SOFIA instrumentation, including a far-infrared
camera for polarimetry.

SOFIA normally flies out of California, but once a year also
deploys to the Southern Hemisphere (usually to Christchurch,
New Zealand), benefitting from the excellent wintertime
stratospheric conditions to study the rich southern skies.


Hans Zinnecker (Deutsches SOFIA Institut, Univ. of Stuttgart, Germany; retired)

Nicolas Clerc : Galaxy cluster cosmology and large X-ray surveys @ Univers 22
Oct 4 @ 11 h 00 min – 12 h 00 min

Clusters of galaxies are the largest (~ Mpc sizes) and the most massive (~1014-15 Msol) structures in the cosmic web. They enclose large quantities of hot baryonic gas emitting copious amounts X-ray photons, which allow to trace massive matter haloes out to large redshifts. For this reason, X-ray galaxy clusters are long-standing probes of the growth of large-scale structure: studies of their distribution in space and in mass are driven by their unique capability in constraining cosmological models and the nature of dark energy. I will select and describe important observational and modeling challenges related to cosmology with X-ray galaxy clusters, by presenting results and forecasts based on ongoing large-area surveys: X-CLASS, the XMM-XXL and SDSS-IV/SPIDERS. In particular, I will demonstrate the ability of a self-consistent approach combining X-rays, optical and weak-lensing measurements to study cosmological parameters and physical scaling relations of X-ray clusters.

Laure Ciesla — Spectral Energy Distribution of Galaxies: a tool to probe their star formation histories @ Univers
Oct 18 @ 11 h 00 min – 12 h 00 min

With the wealth of ancillary data available in large domains of the 
spectrum (GALEX, HST, CFHT, Spitzer, Herschel, etc), panchromatic studies of 
galaxies are thus one of the keys to understand how galaxies evolved since their 
formation. After describing the assets of spectral energy distributions (SED) 
analysis and explaining how we can model them, I will discuss the star formation history of the 
bulk of galaxies and show with a concrete case 
how we can identify and characterize galaxies 
than underwent a rapid star 
formation quenching with a sample of well-known local galaxies, the Herschel 
Reference Survey. This sample contains galaxies from the field but also from the 
dense environment of the Virgo cluster. From this pilot study, I will go to 
higher redshifts in order to blindly identify sources that have just been 
quenched using CANDELS/GOODS-South data and try to identify possible causes for 

Séminaire : Pascal Rosenblatt @ Univers 21
Nov 8 @ 11 h 00 min – 12 h 00 min


Sebastien Wolf @ Univers
Fév 28 @ 11 h 00 min – 12 h 00 min