Cold Gas in Massive Galaxies as A Critical Test of Black Hole Feedback Models

TL;DR

This paper evaluates black hole feedback models in galaxy simulations by comparing their predictions of neutral hydrogen gas content with recent observations, finding IllustrisTNG's model aligns best with real data.

Contribution

It introduces a novel observational constraint on black hole feedback models using neutral hydrogen gas measurements in massive galaxies.

Findings

IllustrisTNG's feedback model agrees with observed gas content better than others.

Kinetic winds driven by black holes at low accretion rates are favored.

Supports AGN feedback as a key mechanism for quenching massive galaxies.

Abstract

Black hole feedback has been widely implemented as the key recipe to quench star formation in massive galaxies in modern semi-analytic models and hydrodynamical simulations. As the theoretical details surrounding the accretion and feedback of black holes continue to be refined, various feedback models have been implemented across simulations, with notable differences in their outcomes. Yet, most of these simulations have successfully reproduced some observations, such as stellar mass function and star formation rate density in the local Universe. We use the recent observation on the change of neutral hydrogen gas mass (including both ${\rm H_2}$ and ${\rm HI}$) with star formation rate of massive central disc galaxies as a critical constraint of black hole feedback models across several simulations. We find that the predictions of IllustrisTNG agree with the observations much better than the other models tested in this work. This favors IllustrisTNG's treatment of active galactic nuclei - where kinetic winds are driven by black holes at low accretion rates - as more plausible amongst those we test. In turn, this also indirectly supports the idea that the massive central disc galaxy population in the local Universe was likely quenched by AGN feedback.