#Super masive blackhole Pc#

#Super masive blackhole Pc#

The Keplerian orbital motions of the individual megamaser spots imply a central source mass of 3.6 × 10 7 M ⊙ within the inner 0.1 pc of the galaxy. Probably the best direct evidence is provided by the kinematics of megamasers in the Seyfert 2 galaxy NGC 4268. The argument that supermassive black holes reside in AGNs continues to get stronger. Thus, a modest accretion rate can sustain even high-luminosity QSOs. The mass accretion rate required to sustain the Eddington luminosity can thus be written as dM E/ dt = 2.2( M /10 8) M ⊙ year –1, where M is the mass of the quasar in solar masses. This is therefore a useful benchmark in considering accretion rates and efficiencies. An equivalent way to think of this is to define the Eddington luminosity L E = 1.3 ×10 38 ( M/ M ⊙) ergs s –1, which is the maximum luminosity of a source of mass M that is powered by spherical accretion.

Thus, a bright quasar with a luminosity of 10 46 ergs s –1 must have a mass greater than 10 8 M ⊙. In units appropriate for quasars, M E = 8 × 10 5 (L/10 44) M ⊙ where L is the central source luminosity in units of ergs s –1. That QSOs are massive can be inferred from the Eddington limit, which is the minimum mass required for a gravitationally bound, self-luminous object to be stable against radiation pressure. It was recognized early that gravitational accretion by supermassive black holes was a possible explanation, and indeed this is the only explanation that remains viable after some four decades of research. The quasar problem, as noted above, is to try to explain how such an enormous amount of energy can be generated in such a small volume. Vestergaard, in Encyclopedia of Physical Science and Technology (Third Edition), 2003 II.A Supermassive Black Holes