ZCOSMOS 20k: Satellite galaxies are the main drivers of environmental effects in the galaxy population at least to z ~ 0.7

We explore the role of environment in the evolution of galaxies over 0.1 < z < 0.7 using the final zCOSMOS-bright data set. Using the red fraction of galaxies as a proxy for the quenched population, we find that the fraction of red galaxies increases with the environmental overdensity δ and with the stellar mass M_*, consistent with previous works. As at lower redshift, the red fraction appears to be separable in mass and environment, suggesting the action of two processes: mass ε_m(M_*) and environmental ε_ρ(δ) quenching. The parameters describing these appear to be essentially the same at z ∼ 0.7 as locally. We explore the relation between red fraction, mass and environment also for the central and satellite galaxies separately, paying close attention to the effects of impurities in the central-satellite classification and using carefully constructed samples well matched in stellar mass. There is little evidence for a dependence of the red fraction of centrals on overdensity. Satellites are consistently redder at all overdensities, and the satellite quenching efficiency, ε_sat(δ, M_*), increases with overdensity at 0.1 < z < 0.4. This is less marked at higher redshift, but both are nevertheless consistent with the equivalent local measurements. At a given stellar mass, the fraction of galaxies that are satellites, f_sat(δ, M_*), also increases with overdensity. The obtained ε_ρ(δ)/f_sat(δ, M_*) agrees well with ε_sat(δ, M_*), demonstrating that the environmental quenching in the overall population is consistent with being entirely produced by a satellite quenching process at least up to z = 0.7. However, despite the unprecedented size of our high-redshift samples, the associated statistical uncertainties are still significant and our statements should be understood as approximations to physical reality, rather than physically exact formulae.