Investigating the Impacts of AGN Activities on Dwarf Galaxies with FAST HI Observations

TL;DR

This study uses FAST HI observations to explore how AGN activity influences gas content and star formation in dwarf galaxies, revealing environmental factors as primary quenching agents over AGN effects.

Contribution

It provides the first comprehensive analysis of HI gas and star formation in AGN-hosting dwarf galaxies, highlighting environmental impacts on galaxy evolution.

Findings

AGN are more common in accompanied dwarf galaxies.

AGN-hosting dwarfs have lower HI mass fractions in dense environments.

Star formation decreases with environmental density in AGN-hosting dwarfs.

Abstract

We present the results of Hi line observations towards 26 Active Galactic Nuclei (AGN)-hosting and one star-forming dwarf galaxies (Mstar < 10^9.5 Msun) with the 19-beam spectral line receiver of FAST at 1.4 GHz. Our FAST observed targets are combined with other AGN-hosting dwarf galaxies covered in the ALFALFA footprint to form a more comprehensive sample. Utilizing the information from optical surveys, we further divide them into isolated and accompanied subsamples by their vicinity of nearby massive galaxies. We compare the Hi gas abundance and star-forming rate (SFR) between the subsamples to assess the role of internal and external processes that may regulate the gas content in dwarf galaxies. As a result, we find that AGN are more commonly identified in accompanied dwarf galaxies than in their isolated counterparts. Meanwhile, AGN-hosting dwarf galaxies have slightly but significant lower Hi mass fraction relatively to the non-AGN control sample in accompanied dwarf galaxies. On the other hand, we find a decreasing SFR in AGN-hosting dwarf galaxies towards denser environments, as well as an extremely low incidence of quenched isolated dwarfs within both AGN and non-AGN subsamples. These results indicate that although these AGN could potentially regulate the gas reservoir of dwarf galaxies, environmental effects are likely the dominant quenching mechanism in the low-mass universe.