Group quenching and galactic conformity at low redshift
  We quantify the quenching impact of the group environment using the
spectroscopic survey Galaxy and Mass Assembly (GAMA) to z=0.2. The fraction of
red (quiescent) galaxies, whether in groups or isolated, increases with both
stellar mass and large-scale (5 Mpc) density. At fixed stellar mass, the red
fraction is on average higher for satellites of red centrals than of blue
(star-forming) centrals, a galactic conformity effect that increases with
density. Most of the signal originates from groups that have the highest
stellar mass, reside in the densest environments, and have massive, red only
centrals. Assuming a color-dependent halo-to-stellar-mass ratio, whereby red
central galaxies inhabit significantly more massive halos than blue ones of the
same stellar mass, two regimes emerge more distinctly: at log(Mhalo/Msol) < 13,
central quenching is still ongoing, conformity is no longer existent, and
satellites and group centrals exhibit the same quenching excess over field
galaxies at all mass and density, in agreement with the concept of "group
quenching"; at log(Mhalo/Msol) > 13, a cutoff that sets apart massive
(log(M*/Msol) > 11), fully quenched group centrals, conformity is meaningless,
and satellites undergo significantly more quenching than their counterparts in
smaller halos. The latter effect strongly increases with density, giving rise
to the density-dependent conformity signal when both regimes are mixed. The
star-formation of blue satellites in massive halos is also suppressed compared
to blue field galaxies, while blue group centrals and the majority of blue
satellites, which reside in low mass halos, show no deviation from the
color-stellar mass relation of blue field galaxies.
