A New Sample of Dwarf Galaxies with X-ray-Selected AGN Candidates from the eROSITA All-Sky Survey

Abstract

To investigate the population of massive black holes in dwarf galaxies, we conduct a systematic search for active galactic nuclei (AGNs) using data from the first data release of the eROSITA All-Sky Survey (eRASS1). We crossmatch dwarf galaxy positions in the NASA-Sloan Atlas with X-ray sources from eRASS and apply rigorous criteria to remove contaminants such as background sources, galaxies with dubious stellar masses, and X-ray binaries. Potential contamination from ultraluminous X-ray sources is also assessed. We ultimately assemble a sample of 27 X-ray-selected AGN candidates in dwarf galaxies with stellar masses $M_{*} = 10^{7.5-9.5} M_{\odot}$ and redshifts $z<0.15$. An analysis of the host galaxy properties reveals that the AGN candidates are predominantly situated in systems with $g-r$ colors, star formation rates, and concentrations typical of the broader dwarf galaxy population. Detailed examination of the X-ray sources indicates that most AGN candidates in our sample are consistent with being located in the nuclear regions of their host galaxies and exhibit Eddington ratios ranging between $\lambda_{Edd} \sim 10^{-3}-10^{-1}$, with a few radiating at/above their Eddington limit. Notably, our methodology identifies 15 previously unreported AGNs candidates, highlighting the complementary nature of our approach to the existing literature.