Instruct: Identify the main and secondary category of Arxiv papers based on the titles and abstracts
Query: Star Captures by Quasar Accretion Disks: A Possible Explanation of the
  M-sigma Relation   A new theory of quasars is presented in which the matter of thin accretion
disks around black holes is supplied by stars that plunge through the disk.
Stars in the central part of the host galaxy are randomly perturbed to highly
radial orbits, and as they repeatedly cross the disk they lose orbital energy
by drag, eventually merging into the disk. Requiring the rate of stellar mass
capture to equal the mass accretion rate into the black hole, a relation
between the black hole mass and the stellar velocity dispersion is predicted of
the form M_{BH} \propto sigma_*^{30/7}. The normalization depends on various
uncertain parameters such as the disk viscosity, but is consistent with
observation for reasonable assumptions. We show that a seed central black hole
in a newly formed stellar system can grow at the Eddington rate up to this
predicted mass via stellar captures by the accretion disk. Once this mass is
reached, star captures are insufficient to maintain an Eddington accretion
rate, and the quasar may naturally turn off as the accretion switches to a
low-efficiency advection mode. The model provides a mechanism to deliver mass
to the accretion disk at small radius, probably solving the problem of
gravitational instability to star formation in the disk at large radius. We
note that the matter from stars that is incorporated to the disk has an average
specific angular momentum that is very small or opposite to that of the disk,
and discuss how a rotating disk may be maintained as it captures this matter if
a small fraction of the accreted mass comes from stellar winds that form a disk
extending to larger radius. We propose several observational tests and
consequences of this theory.

22
The categories of this paper are: chao-dyn
14
The categories of this paper are: math-ph
4
The categories of this paper are: cond-mat
11
The categories of this paper are: hep-lat
3
The categories of this paper are: physics
28
The categories of this paper are: alg-geom
25
The categories of this paper are: patt-sol
29
The categories of this paper are: funct-an
13
The categories of this paper are: quant-ph
18
The categories of this paper are: econ
9
The categories of this paper are: nlin
12
The categories of this paper are: nucl-th
7
The categories of this paper are: hep-th
16
The categories of this paper are: stat
1
The categories of this paper are: cs
26
The categories of this paper are: bayes-an