Quenching Star Formation: Can AGN Do the Trick?

TL;DR

This study investigates whether active galactic nucleus (AGN) feedback mechanisms, specifically quasar and radio modes, can effectively quench star formation in galaxies, producing realistic red sequences in simulations.

Contribution

It evaluates the impact of AGN feedback models on galaxy quenching and compares simulation outcomes with SDSS observations to assess their realism.

Findings

Both AGN feedback modes produce a red sequence and match luminosity functions reasonably well.

Galaxies are slightly too blue compared to observations.

Merger-based quasar mode feedback results in an unrealistic red sequence build-up.

Abstract

We post-process galaxy star formation histories in cosmological hydrodynamics simulations to test quenching mechanisms associated with AGN. By comparing simulation results to color-magnitude diagrams and luminosity functions of SDSS galaxies, we examine whether "quasar mode" or "radio mode" AGN feedback can yield a realistic red sequence. Both cases yield red sequences distinct from the blue cloud, decent matches to the luminosity function, and galaxies that are too blue by about 0.1 magnitudes in g-r. Our merger-based prescription for quasar mode feedback, however, yields a red sequence build-up inconsistent with observations: the luminosity function lacks a characteristic knee, and the brightest galaxies include a small number of young stars.