Hot gas in massive halos drives both mass quenching and environment quenching

TL;DR

This study uses cosmological simulations to demonstrate that hot gas in massive halos is a key driver of galaxy quenching, affecting both mass and environment-related processes.

Contribution

It introduces a hot gas quenching model in simulations that successfully reproduces observed galaxy quenching trends across different environments and masses.

Findings

Hot gas in halos >10^12 Msun drives galaxy quenching.

Mass quenching is independent of environment due to large halo mass range.

Environment quenching is independent of stellar mass, affecting satellites across environments.

Abstract

Observations indicate that galaxies with high stellar masses or in dense environments have low specific star formation rates, i.e. they are quenched. Based on cosmological hydrodynamic simulations that include a prescription where quenching occurs in regions dominated by hot (>10^5 K) gas, we argue that this hot gas quenching in halos >10^12 Msun drives both mass quenching (i.e. central quenching) and environment quenching (i.e. satellite quenching). These simulations reproduce a broad range of locally observed trends among quenching, halo mass, stellar mass, environment, and distance to halo center. We show that mass quenching is independent of environment because 10^12-10^13 Msun "quenching halos" -- those where most mass quenching occurs -- inhabit a large range of environments. On the other hand, environment quenching is independent of stellar mass because galaxies of all stellar masses may live in dense environments as satellites of groups and clusters. Furthermore, satellite galaxies show signs of mass quenching independent of halo mass because massive satellites at z=0 have typically been mass quenched as centrals in their own hot halos at higher z -- a kind of pre-processing. As in observations, the fraction of quenched satellites increases with halo mass and decreases with distance to the center of the group or cluster. We investigate quenched centrals in low-mass halos (<10^12 Msun), and show that most of these are ejected former satellites of groups or clusters, while about 20 per cent were never satellites but are enveloped in hot gas that extends up to 3 Rvir from the centers of clusters. The agreement of our model with key observational trends suggests that hot gas in massive halos plays a leading role in quenching low-redshift galaxies.