1205.4021 (A. Raichoor et al.)
A. Raichoor, S. Andreon
Galaxy mass and environment are known to play a key role in galaxy evolution: looking at galaxy colors at different redshifts, fixed galaxy mass and environment, offers a powerful diagnosis to disentangle the role of each. In this work, we study the simulateneous dependence of the fraction of blue galaxies fblue on secular evolution, environment and galaxy mass with a well-controlled cluster sample. We are thus able to study the evolution and respective role of the cessation of star formation history (SFH) in clusters due to galaxy mass ("mass quenching") or to environment ("environmental quenching"). We define an homogenous X-ray selected cluster sample (25 clusters with 0 < z < 1 and one cluster at z \sim 2.2), having similar masses and well-defined sizes. Using multicolor photometry and a large spectroscopic sample to calibrate photometric redshifts, we carefully estimate fblue for each cluster at different galaxy mass and cluster-centric distance bins. We then fit with a simple model the dependence of fblue on redshift (z), environment (r/r200) and galaxy mass (M). fblue increases with cluster-centric distance with a slope $1.2^{+0.4}_{-0.3}$, decreases with galaxy mass with a slope $-3.8^{+0.6}_{-0.5}$, and increases with redshift with a slope $3.2^{+0.7}_{-0.5}$. The data also require for the first time a differential evolution with galaxy mass of fblue with redshift, with lower mass galaxies evolving slower by a factor $-4.1^{+1.1}_{-0.9}$. Our study shows that the processes responsible for the cessation of star formation in clusters are effective at all epochs (z<2.2), and more effective in denser environments and for more massive galaxies. We found that the mass and environmental quenchings are separable, that environmental quenching does not change with epoch, and that mass quenching is a dynamical process, i.e. its evolutionary rate is mass-dependent. [Abridged]
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http://arxiv.org/abs/1205.4021
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