Formation et Evolution des Galaxies - Groupe de Recherche IAP

Date

Sujet

Présenté par

9 février 2012

On the Hot Gas of Early-type Galaxies. Slow versus Fast Rotators

For a galaxy, the ability to sustain a corona of hot, X-ray emitting gas can be a key element determining its star-formation history. An halo of hot gas can indeed be an effective shield against the external acquisition of cold gas whereas stellar-mass loss material is quickly absorbed by such an hot medium.

Since the discovery of such X-ray halos, the origin of the X-ray emission and the precise amount of hot gas around galaxies have been the matter of long debates, in particular when considering the rather loose correlation between the optical and X-ray luminosity of galaxies. This situation resulted from the limited ability to separate with earlier X-ray data the contribution from an active nucleus, the unresolved population of X-ray binaries and the X-ray emission from the intra-cluster medium, although the use of loosely defined optical data may have also contributed to such an impasse.

By combining the homogeneously-derived photometric and kinematic measurements for the 260 early-type galaxies of the Atlas3D integral-field spectroscopic survey with both low- and high-spatial resolution X-ray measurements, I will show that the ability to retain an halo of hot gas depends crucially on the dynamical structure and intrinsic flattening of a galaxy. In fact, in the framework of the revised classification for early-type galaxies advanced by the SAURON survey, I will show that Slow and Fast Rotators have radically different behaviors when it comes to their hot-gas content.

Marc Sarzi
Univ. Herfordshire

Résumé d'un journal-club