Dušan Kereš




How Do Galaxies Get Their Gas?

Most galaxies are actively star forming at all epochs. However, there is not enough gas in galaxies to support evolution of star formation activity over time. This suggests that galactic gas is being replenished from the intergalactic medium.


I use cosmological hydrodynamic simulations to study the physics of gas supply into galactic component. At high redshift infall of cold filamentary gas dominates accretion rates of all galaxies. This "cold mode accretion" differs from the standard model of galaxy formation in which cooling of the hot halo atmospheres is a source of galactic gas. Cold mode accretion is a major driver of active star formation of high-z galaxies enabling such activity to proceed for a significant fraction of the Hubble time. At low redshift hot virialized gas can cool in some of the halos, but gaseous clouds that form in infalling filaments bring the cold gas into galaxies such as Milky Way.

In this talk I will describe properties, physics and consequences of gas accretion processes as well as predictions for a variety of observational probes of cold halo gas that can provide strong constraints on theoretical models. I will also discuss remaining open issues and future directions in studies of galactic gas accretion, including new computational methods and observations with upcoming facilities.