A Deeper Look into eFEDS AGN Candidates in Dwarf Galaxies with Chandra

TL;DR

This study uses Chandra X-ray observations to confirm active galactic nuclei in two dwarf galaxies, providing insights into seed black holes in the early universe by analyzing their X-ray luminosities and estimating black hole masses.

Contribution

First Chandra follow-up of eFEDS dwarf galaxy AGN candidates, confirming AGN presence and estimating black hole properties in low-mass galaxies.

Findings

Detected X-ray sources consistent with AGN in two dwarf galaxies.

Estimated black hole masses around 10^5 to 10^6 solar masses.

Identified a ULX in one galaxy, supporting diverse X-ray sources in dwarf galaxies.

Abstract

The ability to accurately discern active massive black holes (BHs) in nearby dwarf galaxies is paramount to understanding the origins and processes of "seed" BHs in the early Universe. We present Chandra X-ray Observatory observations of a sample of three local dwarf galaxies (M$_{*}$ $\leqslant 3 \times 10^{9}$ M$_\odot$, z $\leqslant$ 0.15) previously identified as candidates for hosting active galactic nuclei (AGN). The galaxies were selected from the NASA-Sloan Atlas (NSA) with spatially coincident X-ray detections in the eROSITA Final Equatorial Depth Survey (eFEDS). Our new Chandra data reveal three X-ray point sources in two of the target galaxies with luminosities between log(L$_{\rm \text{2-10 keV}}$ [erg s$^{-1}$]) = 39.1 and 40.4. Our results support the presence of an AGN in these two galaxies and a ULX in one of them. For the AGNs, we estimate BH masses of $M_{\rm BH} \sim 10^{5-6} M_\odot$ and Eddington ratios on the order of $\sim 10^{-3}$.