2013MNRAS.428.3306W

We study the dependence of star formation quenching on galaxy mass and environment, in the Sloan Digital Sky Survey (SDSS; z ∼ 0.1) and the All-Wavelength Extended Groth Strip International Survey (AEGIS; z ∼ 1). It is crucial that we define quenching by low star formation rate rather than by red colour, given that one-third of the red galaxies are star forming. We address stellar mass M*, halo mass Mh, density over the nearest N neighbours δN and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites quenching also depends on D. We present the M*-Mh relation for centrals at z ∼ 1. At z ∼ 1, the dependence of quenching on M* at fixed Mh is somewhat more pronounced than at z ∼ 0, but the quenched fraction is low (10percent) and the haloes are less massive. For satellites, M*-dependent quenching is noticeable at high D, suggesting a quenching dependence on subhalo mass for recently captured satellites. At small D, where satellites likely fell in more than a few Gyr ago, quenching strongly depends on Mh and not on M*. The Mh dependence of quenching is consistent with theoretical wisdom where virial shock heating in massive haloes shuts down accretion and triggers ram-pressure stripping, causing quenching. The interpretation of δN is complicated by the fact that it depends on the number of observed group members compared to N, motivating the use of D as a better measure of local environment.