Abstract
Using galaxy group/cluster catalogs created from the Sloan Digital Sky Survey
Data Release 7, we examine in detail the specific star formation rate (SSFR)
distribution of satellite galaxies and its dependence on stellar mass, halo
mass, and halo-centric radius. All galaxies, regardless of central-satellite
designation, exhibit a similar bimodal SSFR distribution, with a strong break
at SSFR 10^-11 yr^-1 and the same high SSFR peak; in no regime is there
ever an excess of galaxies in the 'green valley'. Satellite galaxies are simply
more likely to lie on the quenched ('red sequence') side of the SSFR
distribution. Furthermore, the satellite quenched fraction excess above the
field galaxy value is nearly independent of galaxy stellar mass. An enhanced
quenched fraction for satellites persists in groups with halo masses down to 3
10^11 Mand increases strongly with halo mass and toward halo
center. We find no detectable quenching enhancement for galaxies beyond \approx
2Rvir around massive clusters once these galaxies have been decomposed into
centrals and satellites. These trends imply that (1) galaxies experience no
significant environmental effects until they cross within \simRvir of a more
massive halo, (2) after this, star formation in active satellites continues to
evolve in the same manner as active centrals for several Gyrs, and (3) once
begun, satellite star formation quenching occurs rapidly. These results place
strong constraints on satellite-specific quenching mechanisms, as we will
discuss further in a companion paper.
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