The Double Nucleus and Central Black Hole of M31

摘要: New spectroscopy of M31 supports Tremaine's model in which both nuclei are parts a single eccentric disk stars orbiting the black hole (BH). The kinematics and Hubble Space Telescope photometry used to measure offset BH from center mass. This confirms that mass is ~ 3 × 107 M☉ by technique nearly independent stellar-dynamical models. We present nucleus obtained with Canada-France-Hawaii Subarcsecond Imaging Spectrograph. Spectra at Ca infrared triplet lines (seeing σ* = 027) stellar kinematics, spectra Mg I b (σ* 031) metallicities. also nonparametric line-of-sight velocity distributions (LOSVDs). All confirm steep rotation dispersion gradients imply contains 3.3 central dark object. At 027, maximum bulge-subtracted 233 ± 4 km s-1 on P2 side, 287 9 s-1. peak displaced 020 003 direction opposite P1, confirming result Bacon coworkers. higher surface brightness nucleus, colder than bulge, σ 100 r 1''. Cold light P1 contributes center; this explains part σ(r) asymmetry. cold 1'' sides center. Our results test double BH. (1) predicts 02 toward P1. observations show displacement 008 001 before bulge subtraction 010 after subtraction. (2) minimum 135 observe 123 2 Observations may be reconciled if its parameters tweaked so orbital eccentricity made larger orientation orbits point more us. (3) curve asymmetric; perfect resolution, V 60 side side. we an asymmetry 54 regard as confirmation model's essential idea coherently aligned. (4) should have same population. this: similar it or globular cluster M32. makes unlikely consists accreted stars. (5) observation there implies, disk, some escaped P1-P2 alignment phase-mixed around galaxy's coincides ultraviolet-bright seen images. propose cluster. Its 0068 0010 If put object UV adopt dynamically determined mass-to-light ratio stars, then (COM) within 0017 0016. COM agrees outer nucleus. Therefore, our suggestion normal ratio, location BH, largely dynamical implies any alternative less 013 0.49 pc radius. observed M/LV 300 cylinder radius 2200 sphere 013. much previous measurements M/LV. argument greatly strengthen detection M31.