Birth of the Cool
Neal Katz
University of Massachussetts
November 13, 2006, 4PM
There are two ways that a galaxy can acquire gas to form stars: the
accretion of smaller galaxies that contain gas or the smooth accretion of
gas not in galaxies. I will use hydrodynamical simulations of a Lambda
dominated CDM Universe to investigate these issues. Perhaps surprisingly,
most material enters galaxies through smooth accretion and not through
merging. It is commonly believed that gas is shock heated to the virial
temperature as it enters a dark halo and that the rate that smooth gas
accretes onto the galaxy is regulated by the cooling time from the virial
temperature. I will show that there are actually two channels by which
gas can smoothly accrete onto a galaxy: the standard one just mentioned
and one where the gas remains cool and its accretion rate is dominated by
dynamical processes. It is this second process that dominates overall,
particularly at higher redshifts. AGN feedback could suppress or remove
the standard cooling mode. I will present results of what would happen
to the galaxy population if this were to occur.
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