Galaxy | Const | Type | Distance | Luminosity | Mass | DT | Comment | Sources |
---|---|---|---|---|---|---|---|---|
Milky Way | [Sgr] | Sbc | 0.028 | 1.9 | 2 | S | Sgr A, Galactic Center | Genzel et al. 1997; Ghez et al. 1998 |
M31 | And | Sb | 2.9 | 5.2 | 30 | S | Andromeda Galaxy | Dressler/Richstone 1988; Kormendy 1988b |
M32 | And | E2 | 2.9 | 0.25 | 3 | S | Satellite of M31 | Tonry 1984, 1987; Dressler/Richstone 1988 |
NGC 3115 | Sex | SO | 27 | 14.2 | 2 | S | Kormendy & Richstone 1992 | |
M106 | CVn | Sbc | 24 | 1.3 | 40 | M | Miyoshi et al. 1995 | |
NGC 4261 | Vir | E2 | 90 | 33 | 400 | G | Ferrarese et al. 1996 | |
M87 | Vir | E0 | 60 | 56 | 3000 | G | Harms et al. 1994 | |
M104 | Vir | Sa | 50 | 47 | 1000 | S | Sombrero Galaxy | Kormendy 1988c |
NGC 3377 | Leo | E5 | 38 | 5.2 | 100 | S | Kormendy et al. 1998; Richstone et al. 1999 | |
M105 | Leo | E1 | 38 | 13 | 100 | S | Gebhardt et al. 1999 | |
NGC 4486B | Vir | E0 | 60 | 0.82 | 500 | S | Satellite of M87 | Kormendy et al. 1997 |
M77 | Cet | Sb | 60 | 10 | M | Caltech IR detection | Greenhill et al. 1996, NRAO PR Jan 15/2000 | |
M84 | Vir | S0 | 60 | 56 | 300 | G | HST STIS (May 1997) | Bower et al. 1998 |
NGC 4342 | Vir | S0 | 60 | 50 | S | Cretton/van den Bosch 1999 | ||
NGC 7052 | Vul | E4 | 191 | 300 | G | van der Marel/van den Bosch 1998 | ||
NGC 6251 | UMi | E2 | 346 | 600 | G | Ferrarese & Ford 1999 | ||
NGC 4945 | Cen | Scd | 15 | 1 | M | Greenhill et al. 1997 |
Key:
This table summarizes data for some of the well-established massive central objects in the nuclei of galaxies. The masses of these objects are usually estimated from the orbital velocity of stars or gas orbiting the objects at distances of some tens or hundreds of light years, which shows that enormous masses are concentrated in small volumes. Many of these central objects exhibit other signs of violent gravitational action: Accretion disks, emission of strong radio and/or high-energy radiation, or jets of highly accelerated material.
What may be the nature of these mysterious objects ? Many astronomers take it for granted that these objects are supermassive black holes, but none of them is really resolved. To get truely compelling evidence, or better, to reveal the true nature of the massive central objects, a resolution would be required of the order of the Schwarzschild radius (the "horizon" radius of a black hole acording to Einstein's General Relativity theory). The Schwarzschild radius is simply correlated to the mass of an object, as it is defined as that radius where the escape velocity from the mass equals light velocity; this means that it is proportional to the mass. The formal relation can be given as
The table above is partly based on STScI-PR97-01 and John Kormendy's CENSUS of Black Hole Candidates in galactic nuclei (more technical version).
Last Modification: 3 Feb 2000, 17:30 MET