The Nuclear Stellar Disk in Andromeda: A Fossil from the Era of Black
  Hole Growth
  The physics of angular momentum transport from galactic scales (~10-100 pc)
to much smaller radii is one of the oustanding problems in our understanding of
the formation and evolution of super-massive black holes (BHs). Seemingly
unrelated observations have discovered that there is a lopsided stellar disk of
unknown origin orbiting the BH in M31, and possibly many other systems. We show
that these nominally independent puzzles are in fact closely related.
Multi-scale simulations of gas inflow from galactic to BH scales show that when
sufficient gas is driven towards a BH, gravitational instabilities form a
lopsided, eccentric disk that propagates inwards from larger radii. The
lopsided stellar disk exerts a strong torque on the remaining gas, driving
inflows that fuel the growth of the BH and produce quasar-level luminosities.
The same disk can produce significant obscuration along many sightlines and
thus may be the putative 'torus' invoked to explain obscured active galactic
nuclei and the cosmic X-ray background. The stellar relic of this disk is long
lived and retains the eccentric pattern. Simulations that yield quasar-level
accretion rates produce relic stellar disks with kinematics, eccentric
patterns, precession rates, and surface density profiles in reasonable
agreement with observations of M31. The observed properties of nuclear stellar
disks can thus be used to constrain the formation history of super-massive BHs.
