Radio AGN in nearby dwarf galaxies: the important role of AGN in dwarf-galaxy evolution

TL;DR

This study combines optical and radio data to analyze 78 nearby dwarf galaxies with active galactic nuclei (AGN), finding that AGN feedback could significantly influence dwarf galaxy evolution through energetic outputs comparable to their gas reservoirs.

Contribution

It introduces a combined observational and simulation approach to assess AGN activity and feedback in dwarf galaxies, highlighting their potential role in galaxy evolution.

Findings

AGN are common in dwarf galaxies and occur independently of environment or interactions.

Simulated AGN jet powers and energies are sufficient to impact dwarf galaxy gas reservoirs.

AGN feedback plausibly influences dwarf galaxy evolution, similar to massive galaxies.

Abstract

We combine deep optical and radio data, from the Hyper Suprime-Cam and the Low-Frequency Array (LOFAR) respectively, to study 78 radio AGN in nearby (z<0.5) dwarf galaxies. Comparison to a control sample, matched in stellar mass and redshift, indicates that the AGN and controls reside in similar environments, show similar star-formation rates (which trace gas availability) and exhibit a comparable incidence of tidal features (which indicate recent interactions). We explore the AGN properties by combining the predicted gas conditions in dwarfs from a cosmological hydrodynamical simulation with a Monte-Carlo suite of simulated radio sources, based on a semi-analytical model for radio-galaxy evolution. In the subset of LOFAR-detectable simulated sources, which have a similar distribution of radio luminosities as our observed AGN, the median jet powers, ages and accretion rates are $\sim 10^{35}$ W, $\sim 5$ Myr and $\sim 10^{-3.4}$ M$_{\odot}$ yr$^{-1}$ respectively. The median mechanical energy output of these sources is $\sim100$ times larger than the median binding energy expected in dwarf gas reservoirs, making AGN feedback plausible. Since special circumstances (in terms of environment, gas availability and interactions) are not necessary for the presence of AGN, and the central gas masses are predicted to be an order of magnitude larger than that required to fuel the AGN, AGN triggering in dwarfs is likely to be stochastic and a common phenomenon. Together with the plausibility of energetic feedback, this suggests that AGN could be important drivers of dwarf-galaxy evolution, as is the case in massive galaxies.