Galaxy evolution in groups and clusters: satellite star formation
  histories and quenching timescales in a hierarchical Universe
  Satellite galaxies in groups and clusters are more likely to have low star
formation rates (SFR) and lie on the red-sequence than central (field)
galaxies. Using galaxy group/cluster catalogs from SDSS DR7, together with a
cosmological N-body simulation to track satellite orbits, we examine the star
formation histories and quenching timescales of satellites of M_star > 5 x 10^9
M_sun at z=0. We first explore satellite infall histories: group preprocessing
and ejected orbits are critical aspects of satellite evolution, and properly
accounting for these, satellite infall typically occurred at z~0.5, or ~5 Gyr
ago. To obtain accurate initial conditions for the SFRs of satellites at their
time of first infall, we construct an empirical parametrization for the
evolution of central galaxy SFRs and quiescent fractions. With this, we
constrain the importance and efficiency of satellite quenching as a function of
satellite and host halo mass, finding that satellite quenching is the dominant
process for building up all quiescent galaxies at M_star < 10^10 M_sun. We then
constrain satellite star formation histories, finding a 'delayed-then-rapid'
quenching scenario: satellite SFRs evolve unaffected for 2-4 Gyr after infall,
after which star formation quenches rapidly, with an e-folding time of < 0.8
Gyr. These quenching timescales are shorter for more massive satellites but do
not depend on host halo mass: the observed increase in satellite quiescent
fraction with halo mass arises simply because of satellites quenching in a
lower mass group prior to infall (group preprocessing), which is responsible
for up to half of quenched satellites in massive clusters. Because of the long
time delay before quenching starts, satellites experience significant stellar
mass growth after infall, nearly identical to central galaxies. This fact
provides key physical insight into the subhalo abundance matching method.
