Environmental Quenching and Galactic Conformity in the Galaxy
  Cross-Correlation Signal
  It has long been known that environment has a large effect on star formation
in galaxies. There are several known plausible mechanisms to remove the cool
gas needed for star formation, such as strangulation, harassment and
ram-pressure stripping.It is unclear which process is dominant, and over what
range of stellar mass. In this paper, we find evidence for suppression of the
cross-correlation function between massive galaxies and less massive
star-forming galaxies, giving a measure of how less likely a galaxy is to be
star-forming in the vicinity of a more massive galaxy. We develop a formalism
for modelling environmental quenching mechanisms within the Halo Occupation
Distribution scheme. We find that at $z \sim 2$ environment is not a
significant factor in determining quenching of star-forming galaxies, and that
galaxies are quenched with similar probabilities when they are satellites in
sub-group environments, as they are globally. However, by $z \sim 0.5$ galaxies
are much less likely to be star forming when in a high density (group or
low-mass cluster) environment than when not. This increased probability of
being quenched does not appear to have significant radial dependence within the
halo at lower redshifts, supportive of the quenching being caused by the
halting of fresh inflows of pristine gas, as opposed to by tidal stripping.
Furthermore, by separating the massive sample into passive and star-forming, we
see that this effect is further enhanced when the central galaxy is passive, a
manifestation of galactic conformity.
