Galaxy formation in the Planck cosmology - IV. Mass and environmental quenching, conformity and clustering

TL;DR

This paper uses galaxy formation simulations to analyze how star formation quenching depends on stellar mass, environment, and redshift, highlighting the roles of AGN feedback and environmental effects in galaxy evolution.

Contribution

It introduces an updated semi-analytic model within the Planck cosmology framework that reproduces many observed quenching patterns and conformity trends in galaxy populations.

Findings

Quenching efficiency depends on stellar mass, environment, and group properties.

Model reproduces observed galaxy conformity within haloes.

Discrepancies remain in dense regions and near group centers.

Abstract

We study the quenching of star formation as a function of redshift, environment and stellar mass in the galaxy formation simulations of Henriques et al. (2015), which implement an updated version of the Munich semi-analytic model (L-GALAXIES) on the two Millennium Simulations after scaling to a Planck cosmology. In this model massive galaxies are quenched by AGN feedback depending on both black hole and hot gas mass, and hence indirectly on stellar mass. In addition, satellite galaxies of any mass can be quenched by ram-pressure or tidal stripping of gas and through the suppression of gaseous infall. This combination of processes produces quenching efficiencies which depend on stellar mass, host halo mass, environment density, distance to group centre and group central galaxy properties in ways which agree qualitatively with observation. Some discrepancies remain in dense regions and close to group centres, where quenching still seems too efficient. In addition, although the mean stellar age of massive galaxies agrees with observation, the assumed AGN feedback model allows too much ongoing star formation at late times. The fact that both AGN feedback and environmental effects are stronger in higher density environments leads to a correlation between the quenching of central and satellite galaxies which roughly reproduces observed conformity trends inside haloes.