Title: The Birth of the Cool

Abstract: 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. I will discuss how this dichotomy in accretion interacts with the dichotomy feedback processes to produce the observed dichotomies relevant to galaxy formation: red sequence and blue cloud galaxies, bulges and disks, isolated dwarf galaxies that are blue and those that are red, hot core clusters and cool core clusters, etc.