Dependence of Galaxy Quenching on Halo Mass and Distance from its Centre

TL;DR

This study investigates how galaxy star-formation quenching depends on halo mass, galaxy mass, and environment at different redshifts, emphasizing the importance of halo mass and distance from the halo center.

Contribution

It provides new insights into the dependence of galaxy quenching on halo mass and environment, especially highlighting differences between central and satellite galaxies at z~0 and z~1.

Findings

Quenched fraction correlates more strongly with halo mass than galaxy mass.

Quenching in satellites depends on distance from halo center and halo mass.

At higher redshift, the quenched fraction is lower and halo masses are smaller.

Abstract

We study the dependence of star-formation quenching on galaxy mass and environment, in the SDSS (z~0.1) and the AEGIS (z~1). It is crucial that we define quenching by low star-formation rate rather than by red colour, given that one third of the red galaxies are star forming. We address stellar mass M*, halo mass Mh, density over the nearest N neighbours deltaN, and distance to the halo centre D. The fraction of quenched galaxies appears more strongly correlated with Mh at fixed M* than with M* at fixed Mh, while for satellites quenching also depends on D. We present the M*-Mh relation for centrals at z~1. At z~1, the dependence of quenching on M* at fixed Mh is somewhat more pronounced than at z~0, but the quenched fraction is low (10%) and the haloes are less massive. For satellites, M*-dependent quenching is noticeable at high D, suggesting a quenching dependence on sub-halo mass for recently captured satellites. At small D, where satellites likely fell in more than a few Gyr ago, quenching strongly depends on Mh, and not on M*. The Mh-dependence of quenching is consistent with theoretical wisdom where virial shock heating in massive haloes shuts down accretion and triggers ram-pressure stripping, causing quenching. The interpretation of deltaN is complicated by the fact that it depends on the number of observed group members compared to N, motivating the use of D as a better measure of local environment.