Galaxy Evolution in Cosmological Simulations With Outflows I: Stellar
  Masses and Star Formation Rates
  We examine the growth of the stellar content of galaxies from z=3-0 in
cosmological hydrodynamic simulations incorporating parameterised galactic
outflows. Without outflows, galaxies overproduce stellar masses (M*) and star
formation rates (SFRs) compared to observations. Winds introduce a three-tier
form for the galaxy stellar mass and star formation rate functions, where the
middle tier depends on differential (i.e. mass-dependent) recycling of ejected
wind material back into galaxies. A tight M*-SFR relation is a generic outcome
of all these simulations, and its evolution is well-described as being powered
by cold accretion, although current observations at z>2 suggest that star
formation in small early galaxies must be highly suppressed. Roughly one-third
of z=0 galaxies at masses below M^* are satellites, and star formation in
satellites is not much burstier than in centrals. All models fail to suppress
star formation and stellar mass growth in massive galaxies at z<2, indicating
the need for an external quenching mechanism such as black hole feedback. All
models also fail to produce dwarfs as young and rapidly star-forming as
observed. An outflow model following scalings expected for momentum-driven
winds broadly matches observed galaxy evolution around M^* from z=0-3, which is
a significant success since these galaxies dominate cosmic star formation, but
the failures at higher and lower masses highlight the challenges still faced by
this class of models. We argue that central star-forming galaxies are
well-described as living in a slowly-evolving equilibrium between inflows from
gravity and recycled winds, star formation, and strong and ubiquitous outflows
that regulate how much inflow forms into stars. Star-forming galaxy evolution
is thus primarily governed by the continual cycling of baryons between galaxies
and intergalactic gas.
