A Luminous X-Ray Active Galactic Nucleus in the Dwarf-Dwarf Galaxy Merger RGG 66

We present the discovery of a luminous X-ray active galactic nucleus (AGN) in the dwarf galaxy merger RGG 66. The black hole is predicted to have a mass of M BH similar to 105.4 M circle dot and to be radiating close to its Eddington limit (L bol/L Edd similar to 0.75). The AGN in RGG 66 is notable both for its presence in a late-stage dwarf-dwarf merger and for its luminosity of L 2-10 keV = 1042.2 erg s-1, which is among the most powerful AGNs known in nearby dwarf galaxies. The X-ray spectrum has a best-fit photon index of Gamma = 2.4 and an intrinsic absorption of N H similar to 1021 cm-2. These results come from a follow-up Chandra X-ray Observatory study of four irregular/disturbed dwarf galaxies with evidence for hosting AGNs based on optical spectroscopy. The remaining three dwarf galaxies do not have detectable X-ray sources with upper limits of L 2-10 keV less than or similar to 1040 erg s-1. Taken at face value, our results on RGG 66 suggest that mergers may trigger the most luminous of AGNs in the dwarf galaxy regime, just as they are suspected to do in more massive galaxy mergers.