THE EFFECTS OF THE LOCAL ENVIRONMENT AND STELLAR MASS ON GALAXY QUENCHING TO z ∼ 3

We study the effects of the local environment and stellar mass on galaxy properties using a mass complete sample of quiescent and star-forming systems in the COSMOS field at z less than or similar to 3. We show that at z less than or similar to 1 the median star formation rate (SFR) and specific SFR (sSFR) of all galaxies depend on the environment, but they become independent of the environment at z less than or similar to 1. However, we find that only for star-forming galaxies, the median SFR and sSFR are similar in different environments regardless of redshift and stellar mass. We find that the quiescent fraction depends on the environment at z greater than or similar to 1 and on stellar mass out to z similar to 3. We show that at z less than or similar to 1 galaxies become quiescent faster in denser environments and that the overall environmental quenching efficiency increases with cosmic time. Environmental and mass quenching processes depend on each other. At z. 1 denser environments more efficiently quench galaxies with higher masses (log(M/M-circle dot) greater than or similar to 10.7), possibly due to a higher merger rate of massive galaxies in denser environments. We also show that mass quenching is more efficient in denser regions. We show that the overall mass quenching efficiency (epsilon(mass)) for more massive galaxies (log(M/M-circle dot) greater than or similar to 10.2) rises with cosmic time until z similar to 1 and then flattens out. However, for less massive galaxies, the rise in epsilon(mass) continues to the present time. Our results suggest that environmental quenching is only relevant at z less than or similar to 1 and is likely a fast process, whereas mass quenching is the dominant mechanism at z greater than or similar to 1 with a possible stellar feedback physics.