The Origins of AGN Obscuration: The ‘Torus ’ as a Dynamical, Unstable Driver of Accretion

Recent multi-scale simulations have made it possible to follow gas inflows responsible for high-Eddington ratio accretion onto massive black holes (BHs) from galactic scales to the BH accretion disk. When sufficient gas is driven towards a BH, gravitational instabilities generically form lopsided, eccentric disks that propagate inwards from larger radii. The lop-sided stellar disk exerts a strong torque on the gas, driving inflows that fuel the growth of the BH. Here, we investigate the possibility that the same disk, in its gas-rich phase, is the putative “torus ” invoked to explain obscured active galactic nuclei and the cosmic X-ray background. The disk is generically thick and has characteristic ∼ 1 − 10pc sizes and masses resembling those required of the torus. Interestingly, the scale heights and obscured fractions of the pre-dicted torii are substantial even in the absence of strong stellar feedback providing the vertical support. Rather, they can be maintained by strong bending modes and warps/twists excited by the inflow-generating instabilities. A number of other observed properties commonly at-tributed to “feedback ” processes may in fact be explained entirely by dynamical, gravitational effects: the lack of alignment between torus and host galaxy, correlations between local SF