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

TL;DR

This study investigates how environment influences galaxy evolution from redshift 0.1 to 0.7, revealing that satellite quenching predominantly drives environmental effects, with similar processes at play as in the local universe.

Contribution

It demonstrates that environmental quenching in galaxies up to z~0.7 is mainly due to satellite galaxy processes, extending local universe findings to higher redshifts.

Findings

Satellite galaxies are redder at all overdensities.

Satellite quenching efficiency increases with overdensity at 0.1<z<0.4.

Environmental quenching is consistent with satellite quenching up to z~0.7.

Abstract

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 and with the stellar mass, 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 and environmental 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 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 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 also increases with the overdensity. At a given overdensity and mass, the obtained relation between the environmental quenching and the satellite fraction agrees well with the satellite quenching efficiency, demonstrating that the environmental quenching in the overall population is consistent with being entirely produced through the 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.