A little FABLE: exploring AGN feedback in dwarf galaxies with cosmological simulations

TL;DR

This study uses cosmological simulations to explore the role of AGN feedback in dwarf galaxies, revealing that overmassive black holes influence galaxy properties and may be more active at high redshifts, with implications for galaxy evolution.

Contribution

It demonstrates the impact of AGN feedback in dwarf galaxies within cosmological simulations, especially at high redshifts, and compares results with observational data.

Findings

Overmassive black holes drive hotter, faster outflows.

High-redshift dwarfs can host luminous AGN outshining their hosts.

Supernova feedback may suppress low-redshift AGN activity.

Abstract

Contrary to the standard lore, there is mounting observational evidence that feedback from active galactic nuclei (AGN) may also play a role at the low-mass end of the galaxy population. We investigate this using the cosmological simulation suite FABLE, with a particular focus on the dwarf regime ($M_\mathrm{stellar} < 10^{9.5} \ \mathrm{M_{\odot}}$). We find that overmassive black holes (BHs), with respect to the mean scaling relations with their host galaxies, drive hotter and faster outflows and lead to significantly reduced gas mass fractions. They are also more likely to display a kinematically misaligned ionized gas component in our mock MaNGA velocity maps, although we caution that cosmic inflows and mergers contribute to misalignments as well. While in the local Universe the majority of AGN in dwarfs are much dimmer than the stellar component, for $z \geq 2$ there is a significant population that outshines their hosts. These high-redshift overmassive BHs contribute to the quenching of dwarfs, whereas at late cosmic times supernova (SN) feedback is more efficient. While our results are overall in good agreement with X-ray observations of AGN in dwarfs, the lack of high-luminosity X-ray AGN in FABLE at low redshifts highlights an interesting possibility that SN feedback could be too strong in FABLE's dwarfs, curtailing AGN growth and feedback. We predict that future observations may uncover many more AGN in dwarfs with lower luminosities and at higher redshifts.