# AGN in dwarf galaxies: frequency, triggering processes and the plausibility of AGN feedback

## TL;DR

This study investigates the prevalence, triggering mechanisms, and potential feedback effects of AGN in dwarf galaxies, revealing high black hole occupation, secular triggering processes, and significant energetic influence comparable to supernovae.

## Contribution

It provides the first comprehensive analysis of AGN in dwarf galaxies using optical and infrared data, highlighting high occupation fractions and secular triggering processes.

## Key findings

- Infrared AGN fractions are 10-30% in dwarfs.
- Merger fraction in dwarf AGN (~6%) shows no excess.
- AGN luminosities exceed supernova luminosities, especially in dwarfs.

## Abstract

While AGN are considered to be key drivers of the evolution of massive galaxies, their potentially significant role in the dwarf-galaxy regime (M*< 10^9 MSun) remains largely unexplored. We combine optical and infrared data, from the Hyper Suprime-Cam (HSC) and the Wide-field Infrared Explorer (WISE) respectively, to explore the properties of ~800 AGN in dwarfs at low redshift (z<0.3). Infrared-selected AGN fractions are ~10-30 per cent in dwarfs, which, for reasonable duty cycles, indicates a high BH-occupation fraction. Visual inspection of the deep HSC images indicates that the merger fraction in dwarf AGN (~6 per cent) shows no excess compared to a control sample of non-AGN, suggesting that the AGN-triggering processes are secular in nature. Energetic arguments indicate that, in both dwarfs and massive galaxies, bolometric AGN luminosities (L_AGN) are significantly greater than supernova luminosities (L_SN). L_AGN/L_SN is, in fact, higher in dwarfs, with predictions from simulations suggesting that this ratio only increases with redshift. Together with the potentially high BH-occupation fraction, this suggests that, if AGN feedback is an important driver of massive-galaxy evolution, the same is likely to be true in the dwarf regime, contrary to our classical thinking.