Star-formation rates of cluster galaxies: Nature versus nurture

We analysed 17 galaxy clusters, and investigated, for the first time, the dependence of the star formation rate (SFR) and specific star formation rate (sSFR) as a function of projected distance (as a proxy for environment) and stellar mass for cluster galaxies in an intermediate-to-high redshift range (0.4 < Ζ < 0.9). We used up to nine flux points (BVRIZYJHKs magnitudes), its errors, and redshifts to compute M_star, SFR, and sSFR through the spectral energy distribution fitting technique. We use a z-dependent sSFR value to distinguish star-forming (SF) from quiescent galaxies. To analyse the SFR and sSFR history we split our sample into two redshift bins: galaxies at 0.4 < Ζ < 0.6 and 0.6 < Ζ < 0.9. We separate the effects of environment and stellar mass on galaxies by comparing the properties of SF and quiescent galaxies at fixed environment (projected radius) and fixed stellar mass. For the selected spectroscopic sample of more than 500 galaxies, the well-known correlation between SFR and M_star is already in place at z ~ 0.9, for both SF and quenched galaxies. Our results are consistent with no evidence that SFR (or sSFR) depends on environment, suggesting that for cluster galaxies at an intermediate-to-high redshift range, mass is the primary characteristic that drives SFR.