Exploring the Limits of AGN Feedback: Black Holes and the Star Formation Histories of Low-mass Galaxies

Energy feedback, either from active galactic nuclei (AGNs) or from supernovae, is required to understand galaxy formation within a Λ-cold dark matter cosmology. We study a sample of 127 low-mass galaxies, comparing their stellar population 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 -σ relation marks a transitional stellar mass, M _trans = (3.4 ± 2.1) × 10¹⁰ {M}_⊙ , 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 toward a supernovae-driven regime in low-mass systems, as suggested by numerical simulations.