A Normal Supermassive Black Hole in NGC 1277

Abstract

The identification of galaxies with “overly massive” black holes requires two measurements: a black hole mass (M_bh) and a host spheroid mass ({M}_{{sph,\ast }}). Here we provide our measurements for NGC 1277. Our structural decomposition reveals that NGC 1277 is dominated by a “classical” spheroid with a Sérsic index n = 5.3, a half-light radius {R}_{{e,major}}=2.1 {{kpc}}, and a stellar mass of 2.7× {10}¹¹\quad {M}_⊙ (using {M}_*/{L}_V=11.65, Martín-Navarro et al.). This mass is an order of magnitude greater than originally reported. Using the latest M_bh-n, M_bh-{M}_{{sph,\ast }}, and M_bh-σ relations, the expected black hole mass is, respectively, ({0.57}_-0.40^+1.29)× {10}⁹\quad {M}_⊙ , ({1.58}_-1.13^+4.04)× {10}⁹\quad {M}_⊙ , and ({2.27}_-1.44^+4.04)× {10}⁹\quad {M}_⊙ (using σ = 300 km s^-1) for which the “sphere-of-influence” is 0.″31. Our new kinematical maps obtained from laser guide star assisted, adaptive optics on the Keck I Telescope dramatically reaffirm the presence of the inner, nearly edge-on, disk seen in the galaxy image. We also report that this produces a large velocity shear (∼400 km s^-1) across the inner 0.″2 (70 pc) plus elevated values of \sqrt{{σ }²+{V}²} across the inner (+/- 3\buildrel{\prime\prime}\over{.} 8)× (+/- 0\buildrel{\prime\prime}\over{.} 6) region of the galaxy. Our new multi-Gaussian expansion (MGE) models and Jeans Anisotropic MGE analysis struggled to match this extended component. Our optimal black hole mass, albeit a probable upper limit because of the disk is 1.2 × 10⁹ M_⊙ (M/{L}_V=12.3). This is an order of magnitude smaller than originally reported and 4 times smaller than recently reported. It gives an {M}_{{bh}}/{M}_{{sph,\ast }} ratio of 0.45% in agreement with the median (≈0.5%) and range (0.1%-5.0%) observed in non-dwarf, early-type galaxies. This result highlights the need for caution with inner disks.