Abstract
We extend the phenomenological study of the evolving galaxy population of
Peng et al (2010) to the central/satellite dichotomy in Yang et al. SDSS
groups. We find that satellite galaxies are responsible for all the
environmental effects in our earlier work. The fraction of centrals that are
red does not depend on their environment but only on their stellar masses,
whereas that of the satellites depends on both. We define a relative satellite
quenching efficiency epsilon_sat, which is the fraction of blue centrals that
are quenched upon becoming the satellite of another galaxy. This is shown to be
independent of stellar mass, but to depend strongly on local overdensity,
delta, ranging between 0.2 and at least 0.8. The red fraction of satellites
correlate much better with the local over-density delta, a measure of location
within the group, than with the richness of the group, i.e. dark matter halo
mass. This, and the fact that satellite quenching depends on local density and
not on either the stellar mass of the galaxy or the dark matter halo mass gives
clues as to the nature of the satellite-quenching process. We furthermore show
that the mass-quenching of satellite galaxies is also independent of the dark
matter mass of the parent halo. We then apply the Peng et al (2010) approach to
predict the mass functions of central and satellite galaxies, split into
passive and active galaxies, and show that these match very well the observed
mass functions from SDSS, further strengthening the validity of this
phenomenological approach. We highlight the fact that the observed M* is
exactly the same for the star-forming centrals and satellites, which emphasizes
the universality of the mass-quenching process that we identified in Peng et al
(2010). Post-quenching merging modifies the mass function of the central
galaxies but can increase the mass of typical centrals by only about 25%.
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