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Astronomy Colloquium
Gas Accretion in Galaxies
Date: Thursday, December 9th
Time: 3:30 pm
Place: 4421 Sterling Hall
Speaker: Dusan Keres, Harvard Smithsonian Center for Astrophysics
Abstract: &quot;Most galaxies are actively star forming at all epochs. However, observations of dense, galactic gas indicate that, at any epoch, 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.<br>
I use fully cosmological simulations of galaxy formation to study the gas supply into galactic component from high redshift to present. At high redshift &quot;smooth&quot; infall of cold filamentary gas dominates the gas supply of all galaxies. This &quot;cold mode accretion&quot; is unlike the accretion in the standard model of galaxy formation in which cooling of the hot halo atmospheres is a source of gas supply to galaxies. 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. At low redshift hot virialized gas can cool in some of the halos, but cold gaseous clouds that form from infalling filaments can dominate gas supply in galaxies such as Milky Way.<br>
In this talk I will describe properties, physics and consequences of cold gas accretion from the intergalactic medium as well as predictions for the observational probes of cold halo gas that can provide strong constraints on the models. I will also discuss remaining open questions and future directions in the studies of galactic gas accretion, including new computational methods and observations with upcoming facilities.&quot;<br>
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