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