Dynamics of Accretion Flows Irradiated by a Quasar

We present the results from axisymmetric time-dependent HD calculations ofgas flows which are under the influence of gravity of a black hole in quasars.We assume that the flows are non-rotating and exposed to quasar radiation. Wetake into account X-ray heating and the radiation force due to electronscattering and spectral lines. To compute the radiation field, we consider astandard accretion disk as a source of UV photons and a spherical centralobject as a source of X-rays. The gas temperature and ionization state in theflow are calculated self-consistently from the photoionization and heating rateof the central object. We find that for a 10e8 MSUN black hole with anaccretion luminosity of 0.6 of the Eddington luminosity the flow settles into asteady state and has two components: (1) an equatorial inflow and (2) a bipolarinflow/outflow with the outflow leaving the system along the disk rotationalaxis. The inflow is a realization of a Bondi-like accretion flow. The secondcomponent is an example of a non-radial accretion flow which becomes an outflowonce it is pushed close to the rotational axis where thermal expansion and theradiation pressure accelerate it outward. Our main result is that the existenceof the above two flow components is robust to the outer boundary conditions andthe geometry and spectral energy distribution of the radiation field. However,the flow properties are not robust. In particular, the outflow power andcollimation is higher for the radiation dominated by the UV/disk emission thanfor the radiation dominated by the X-ray/central engine emission. Our mostintriguing result is that a very narrow outflow driven by radiation pressure onlines can carry more energy and mass than a broad outflow driven by thermalexpansion.Comment: 14 pages, 4 figures, accepted for publication in Ap