An Accreting, Anomalously Low-mass Black Hole at the Center of Low-mass Galaxy IC 750статьяИсследовательская статья
Статья опубликована в высокорейтинговом журнале
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Дата последнего поиска статьи во внешних источниках: 2 сентября 2020 г.
Аннотация:We present a multiwavelength study of the active galactic nucleus in the nearby (D = 14.1 Mpc) low-mass galaxy IC 750, which has circumnuclear 22 GHz water maser emission. The masers trace a nearly edge-on, warped disk ∼0.2 pc in diameter, coincident with the compact nuclear X-ray source that lies at the base of the ∼kiloparsec-scale extended X-ray emission. The position-velocity structure of the maser emission indicates that the central black hole (BH) has a mass less than 1.4 x 10^5 Msun. Keplerian rotation curves fitted to these data yield enclosed masses between 4.1 x 10^4 Msun and 1.4 x 10^5 Msun, with a mode of 7.2 x 10^4 Msun. Fitting the optical spectrum, we measure a nuclear stellar velocity dispersion σ_star=110.7+12.1−13.4 km/ s. From near-infrared photometry, we fit a bulge mass of (7.3 ± 2.7) x 10^8 Msun and a stellar mass of 1.4 x 10^10 Msun. The mass upper limit of the intermediate-mass BH in IC 750 falls roughly two orders of magnitude below the MBH-σ_star relation and roughly one order of magnitude below the MBH-MBulge and MBH-M* relations—larger than the relations' intrinsic scatters of 0.58 ± 0.09 dex, 0.69 dex, and 0.65 ± 0.09 dex, respectively. These offsets could be due to larger scatter at the low-mass end of these relations. Alternatively, BH growth is intrinsically inefficient in galaxies with low bulge and/or stellar masses, which causes the BHs to be undermassive relative to their hosts, as predicted by some galaxy evolution simulations.