EVIDENCE FOR A SUPERMASSIVE BLACK-HOLE IN NGC-3115

被引:105
作者
KORMENDY, J
RICHSTONE, D
机构
[1] UNIV HAWAII,INST ASTRON,HONOLULU,HI 96822
[2] INST ADV STUDY,PRINCETON,NJ 08540
[3] UNIV MICHIGAN,DEPT ASTRON,ANN ARBOR,MI 48109
关键词
BLACK HOLE PHYSICS; GALAXIES; ELLIPTIC AND LENTICULAR; CD; INDIVIDUAL; (NGC-3115); KINEMATICS AND DYNAMICS; NUCLEI; PHOTOMETRY;
D O I
10.1086/171528
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
Stellar rotation velocities and velocity dispersions along the major and minor axes of the edge-on SO galaxy NGC 3115 have been measured in effective seeing sigma* = 0".42-0".69 with the Canada-France-Hawaii Telescope. Also, V-band surface photometry has been obtained in seeing sigma* = 0".33-0".48. The kinematic data show an unresolved rise in rotation velocity to V = 165 +/- 4 km s-1 at 2" and a 62% increase in velocity dispersion at r < 2". The central dispersion, sigma = 295 +/- 9 km s-1, is well above the scatter in the Faber-Jackson correlation between sigma and bulge luminosity. It is similarly high in the correlation between sigma and core radius. Since the core radius and central surface brightness are normal, this implies that the central mass-to-light ratio is unusually high. To search for a central black hole, we derive three-dimensional velocity and velocity dispersion fields that fit the observations after projection and seeing convolution. Models with isotropic velocity dispersions imply that the mass-to-light ratio rises by more than a factor of 10 at r < 2" to values M/L(V) > 50 much larger than those of old stellar populations. This is a robust result independent of uncertainties in the unprojected kinematics or brightness distribution. Maximum entropy dynamical models are used to investigate the effects of velocity anisotropy. These also fail to fit the kinematics unless there is a rise in M/L(V) toward the center. The smallest central dark mass that gives a good fit to the observations is M. congruent-to 1 x 10(8) M.. However, the tensor virial theorem suggests that the bulge is nearly isotropic. Then the observations imply that NGC 3115 contains a central dark object, possibly a black hole, of mass M. approximately 1 to 2 x 10(9) M..
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页码:559 / 578
页数:20
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