2015ApJ...810...90L

Using a stellar mass-limited sample of ∼46,600 galaxies (M_* > 10^9.1 M_☉) at 0.5 <z < 2, we show that the stellar mass, rather than the environment, is the main parameter controlling quenching of star formation in galaxies with M_* > 10¹⁰ M_☉ out to z = 2. On the other hand, the environmental quenching becomes efficient at z < 1 regardless of galaxy mass, and it serves as a main mechanism for quenching star formation for lower mass galaxies. Our result is based on deep optical and near-infrared imaging data over 2800 arcmin², enabling us to negate cosmic variance and identify 46 galaxy cluster candidates with M ∼ 10¹⁴. From M_* ∼ 10^9.5 to 10^10.5 M_☉, the fraction of quiescent galaxies increases by a factor of ∼10 over the entire redshift range, but the difference between cluster and field environment is negligible. Rapid evolution in the quiescent fraction is seen from z = 2 to z = 1.3 for massive galaxies, suggesting a build-up of massive quiescent galaxies at z >1.3. For galaxies with M_* < 10¹⁰ M_☉ at z < 1.0, the quiescent fraction is found to be as much as a factor of 2 larger in clusters than in field, showing the importance of environmental quenching in low-mass galaxies at low redshift. Most high-mass galaxies are already quenched at z > 1, therefore environmental quenching does not play a significant role for them, although the efficiency of environmental quenching is nearly identical between high- and low-mass galaxies.