The Growth of Red Sequence Galaxies in a Cosmological Hydrodynamic Simulation

TL;DR

This study uses a cosmological hydrodynamic simulation with a star formation quenching model to explore the growth and properties of red sequence galaxies, matching observed trends and providing insights into galaxy evolution.

Contribution

It introduces a heuristic quenching prescription based on hot gas halos that reproduces the observed growth and environmental dependence of red sequence galaxies.

Findings

Red sequence galaxies first quench at stellar masses around 10^10.5 M⊙ at z > 2.

Minor mergers contribute significantly to size growth after galaxies join the red sequence.

The model reproduces local universe mass-density and colour-density relations with minimal evolution to z=1.

Abstract

We examine the cosmic growth of the red sequence in a cosmological hydrodynamic simulation that includes a heuristic prescription for quenching star formation that yields a realistic passive galaxy population today. In this prescription, halos dominated by hot gas are continually heated to prevent their coronae from fueling new star formation. Hot coronae primarily form in halos above \sim10^12 M\odot, so that galaxies with stellar masses \sim10^10.5 M\odot are the first to be quenched and move onto the red sequence at z > 2. The red sequence is concurrently populated at low masses by satellite galaxies in large halos that are starved of new fuel, resulting in a dip in passive galaxy number densities around \sim10^10 M\odot. Stellar mass growth continues for galaxies even after joining the red sequence, primarily through minor mergers with a typical mass ratio \sim1:5. For the most massive systems, the size growth implied by the distribution of merger mass ratios is typically \sim2\times the corresponding mass growth, consistent with observations. This model reproduces mass-density and colour-density trends in the local universe, with essentially no evolution to z = 1, with the hint that such relations may be washed out by z \sim 2. Simulated galaxies are increasingly likely to be red at high masses or high local overdensities. In our model, the presence of surrounding hot gas drives the trends with both mass and environment.