The dependence of low redshift galaxy properties on environment

TL;DR

This review discusses how galaxy properties at low redshift depend on environment, highlighting differences between centrals and satellites, and suggesting starvation and tidal forces as key mechanisms.

Contribution

It synthesizes recent observational results on environmental effects on galaxy properties and proposes that starvation and tidal stripping are primary processes involved.

Findings

Satellite galaxies differ more from centrals in massive haloes

Environmental effects are consistent with starvation as the main mechanism

Impact of environment appears independent of stellar mass

Abstract

We review recent results on the dependence of various galaxy properties on environment at low redshift. As environmental indicators, we use group mass, group-centric radius, and the distinction between centrals and satellites; examined galaxy properties include star formation rate, colour, AGN fraction, age, metallicity and concentration. In general, satellite galaxies diverge more markedly from their central counterparts if they reside in more massive haloes. We show that these results are consistent with starvation being the main environmental effect, if one takes into account that satellites that reside in more massive haloes and at smaller halo-centric radii on average have been accreted a longer time ago. Nevertheless, environmental effects are not fully understood yet. In particular, it is puzzling that the impact of environment on a galaxy seems independent of its stellar mass. This may indicate that the stripping of the extended gas reservoir of satellite galaxies predominantly occurs via tidal forces rather than ram-pressure.