HSC-XD 52: An X-Ray Detected AGN in a Low-mass Galaxy at z ∼ 0.56
Johnson, Sean D.; Sawicki, Marcin; Gwyn, Stephen; Moutard, Thibaud; Toba, Yoshiki; Goulding, Andy; Coupon, Jean; Suh, Hyewon; Greene, Jenny; Golob, Anneya; Halevi, Goni
United States, Switzerland, Canada, Japan, Taiwan
Abstract
The properties of low-mass galaxies hosting central black holes provide clues about the formation and evolution of the progenitors of supermassive black holes. In this Letter, we present HSC-XD 52, a spectroscopically confirmed low-mass active galactic nucleus (AGN) at an intermediate redshift of z ∼ 0.56. We detect this object as a very luminous X-ray source coincident with a galaxy observed by the Hyper Suprime-Cam (HSC) as part of a broader search for low-mass AGN. We constrain its stellar mass through spectral energy distribution modeling to be LMC-like at M ⋆ ≈ 3 × 109 M ⊙, placing it in the dwarf regime. We estimate a central black hole mass of M BH ∼ 106 M ⊙. With an average X-ray luminosity of {L}{{X}}≈ 3.5× {10}43 {erg} {{{s}}}-1, HSC-XD 52 is among the most luminous X-ray selected AGN in dwarf galaxies. The spectroscopic and photometric properties of HSC-XD 52 indicate that it is an intermediate-redshift counterpart to local low-mass AGN.