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تسجيل مستخدم جديدAn Accreting, Anomalously Low Mass Black Hole at the Center of Low Mass Galaxy IC 750
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We present a multi-wavelength 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 $sim$0.2 pc in diameter, coincident with the compact nuclear X-ray source which lies at the base of the $sim$kpc-scale extended X-ray emission. The position-velocity structure of the maser emission indicates the central black hole (BH) has a mass less than $1.4 times 10^5~M_odot$. Keplerian rotation curves fitted to these data yield enclosed masses between $4.1 times 10^4~M_odot$ and $1.4 times 10^5~M_odot$, with a mode of $7.2 times 10^4~M_odot$. Fitting the optical spectrum, we measure a nuclear stellar velocity dispersion $sigma_* = 110.7^{+12.1}_{-13.4}$~{rm km~s}$^{-1}.$ From near-infrared photometry, we fit a bulge mass of $(7.3 pm 2.7) times 10^8~M_odot$ and a stellar mass of $1.4 times 10^{10}~M_odot$. The mass upper limit of the intermediate mass black hole in IC 750 falls roughly two orders of magnitude below the $M_{rm BH}-sigma_*$ relation and roughly one order of magnitude below the $M_{rm BH}-M_{rm Bulge}$ and $M_{rm BH}-M_*$ relations -- larger than the relations intrinsic scatters of (0.58 $pm$ 0.09) dex, 0.69 dex, and (0.65 $pm$ 0.09) dex, respectively. These offsets could be due to larger scatter at the low mass end of these relations. Alternatively, black hole growth is intrinsically inefficient in galaxies with low bulge and/or stellar masses, which causes the black holes to be under-massive relative to their hosts, as predicted by some galaxy evolution simulations.
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