Pierre Guillard // Sébastien Renaux-Petel
Institut d'Astrophysique de Paris (Paris, France)
Models of hierarchical structure formation predict well the spatial distribution of galaxies, but have two global issues at reproducing their physical properties: (1) the "over-cooling problem": according to models, 40-80% of the baryons should be in collapsed structures (clouds and stars), but the observed fraction is <20%. (2) the "broken hierarchy" problem: the most massive galaxies in the local universe have old stellar populations that formed quickly at high redshift, with very little subsequent star-formation, which is in contradiction with the standard bottom-up mass assembly. Amongst many physical processes proposed to limit the gas collapse and star formation, the cascade of turbulent energy in the dense gas is the least explored. I will show how spectroscopic observations of galaxy interactions and active galaxy nuclei (AGN), combined with modeling of the gas physics, can provide information about the role of turbulence in controling the gas heating/cooling balance and the formation of gravitationnally-bound structures at all scales. This has consequences on our understanding of how the kinetic energy released by mergers, AGN feedback and gas accretion onto halos of galaxies impact on the regulation of star formation.
Amphithéâtre Henri Mineur, Institut d'Astrophysique de Paris