A normal supermassive black hole in NGC 1277

TL;DR

This study accurately measures the black hole and host galaxy properties of NGC 1277, revealing a typical black hole mass for its spheroid and emphasizing the importance of detailed structural analysis in such measurements.

Contribution

It provides revised measurements of NGC 1277's black hole and spheroid, demonstrating the black hole is not overly massive, and underscores the significance of accounting for inner disks in such analyses.

Findings

Black hole mass is approximately 1.2x10^9 M_sun.

Spheroid mass is about 2.7x10^{11} M_sun.

Black hole to spheroid mass ratio is 0.45%.

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,*). Here we provide our measurements for NGC 1277. Our structural decomposition reveals that NGC 1277 is dominated by a `classical' spheroid with a Sersic index n=5.3, a half-light radius R_e=2.1 kpc, and a stellar mass of 2.7x10^{11} M_sun (using M_*/L_V=11.65, Martin-Navarro et al.). This mass is an order of magnitude greater than originally reported. Using the latest (M_bh)-n, (M_bh)-(M_sph,*) and (M_bh)-sigma relations, the expected black hole mass is respectively (0.57^{+1.29}_{-0.40})x10^9 M_sun, (1.58^{+4.04}_{-1.13})x10^9 M_sun, and (2.27^{+4.04}_{-1.44})x10^9 M_sun (using sigma=300 km/s) 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 this galaxy's image. We also report that this produces a large velocity shear (~400 km/s) across the inner 0".2 (70 pc) plus elevated values of sqrt{sigma^2+(V_rot)^2} across the inner 3".8x0".6 region of the galaxy. Our new multi-Gaussian expansion (MGE) models and Jeans Anisotropic MGE (JAM) analysis struggled to match this extended component. Our optimal black hole mass, albeit a probable upper limit because of the disk, is 1.2x10^9 M_sun (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,* ratio of 0.45% in agreement with the median (~0.5%) and range (0.1 to 5.0%) observed in non-dwarf, early-type galaxies. This result highlights the need for caution with inner disks.