Exploring the limits of AGN feedback: black holes and the star formation histories of low-mass galaxies

TL;DR

This study investigates how active galactic nuclei (AGN) feedback influences star formation in low-mass galaxies, finding limited impact of AGN activity and identifying a transitional stellar mass where feedback mechanisms shift.

Contribution

It provides observational evidence for a transition in feedback processes at a specific stellar mass, supporting a bi-modal galaxy formation model.

Findings

Weak correlation between black hole mass and star formation history

Identification of a transitional stellar mass at ~3.4×10^{10} M_sun

Support for a shift from AGN to supernova feedback in low-mass galaxies

Abstract

Energy feedback, either from active galactic nuclei (AGN) or from supernovae, is required to understand galaxy formation within a $\Lambda$-Cold Dark Matter cosmology. We study a sample of 127 low-mass galaxies, comparing their stellar populations properties to the mass of the central supermassive black hole, in order to investigate the effect of AGN feedback. We find a loose coupling between star formation history and black hole mass, which seems to suggest that AGN activity does not dominate baryonic cooling in low-mass galaxies. We also find that a break in the $M_\bullet$-$\sigma$ relation marks a transitional stellar mass, M$_\mathrm{trans}=3.4\pm2.1 \times 10^{10}$ M$_{\odot}$, remarkably similar to M$_\star$. Our results are in agreement with a bi-modal star formation process where the AGN-dominated feedback of high-mass galaxies transitions towards a supernovae-driven regime in low-mass systems, as suggested by numerical simulations.