Red Galaxies from Hot Halos in Cosmological Hydro Simulations

TL;DR

This paper uses cosmological hydrodynamic simulations to show that hot halo starvation, not major mergers, causes galaxy quenching, and explains why massive or dense environment galaxies are red.

Contribution

It demonstrates that hot halo starvation, rather than major mergers, is the primary mechanism for galaxy quenching in simulations.

Findings

Starvation in hot halos causes galaxy quenching.

Massive galaxies grow mainly via minor mergers after quenching.

Hot halo quenching explains red galaxies in dense environments.

Abstract

I highlight three results from cosmological hydrodynamic simulations that yield a realistic red sequence of galaxies: 1) Major galaxy mergers are not responsible for shutting off star-formation and forming the red sequence. Starvation in hot halos is. 2) Massive galaxies grow substantially (about a factor of 2 in mass) after being quenched, primarily via minor (1:5) mergers. 3) Hot halo quenching naturally explains why galaxies are red when they either (a) are massive or (b) live in dense environments.