Internal Dynamics and Formation of Emission Clouds in Active Galactic Nuclei
We show that cool UV accretion disks, if present in active galactic nuclei, can be sources of line driven winds. Continuum subcritical disks are shown to possess optically thin continuum winds which are accelerated by radiation pressure in lines.
Results of numerical simulation of outflows from disks around supermassive black holes are presented. The necessary condition for wind initiation is the existence of an appropriate circumstance in which the absorption lines coincide with the radiation peak. Such a situation is shown to arise in the shielded region of the disk, the shield being provided by the disk atmosphere.
The winds are characterized by steep velocity gradients and high asymptotic velocities v/c ∼ 1/30, as observed in broad emission-line regions of OSO’s and Seyfert galaxies, and are thermally unstable as they heat up. This results in a two-phase equilibrium: cold clouds embedded in a hot, Compton-heated background. The hot wind provides the pressure confinement for the dense and massive clouds.
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