Cold Mode of Gas Accretion
Dusan Keres (Harvard) - Oct 12, 2009 at 12:10 pm
Most galaxies are actively star forming at all epochs. However,
observations of cold gas reservoirs indicate that, at any epoch, there
is not enough gas in dense galactic component to support evolution of
star formation activity over time. This suggests that galactic gas is
being replenished from the intergalactic medium.
I use fully cosmological simulations of galaxy
formation to study the gas supply into galactic component from high
redshift to present. At high redshift "smooth" infall of cold
filamentary gas dominates the gas supply of all galaxies. This "cold
mode accretion" is a major driver of very active star formation
of high-z galaxies enabling such activity to proceed for a significant
fraction of the Hubble time. Gas accretion rates at a given halo and
galaxy mass decrease with time, causing the drop in star formation
rates. Properties and geometry of infalling gas change with halo mass
and redshift. At low redshift some of the halos are able to cool hot
virialized gas but filaments are still indirectly supplying galaxies with
gas via cold gaseous clouds that form from infaling cold/warm filamentary
gas.
In this talk I will describe properties, physics and consequences of
gas accretion, and feedback processes needed to modulate growth of
galaxies over time. Finally, I will point out promising directions for
future research in this area and discuss several observational probes
of cold halo gas that can provide strong constraints on the physics of
gas accretion in galaxies.
The seminar will be held in 544 Campbell Hall.
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