Publication Date:
2016-06-02
Description:
We explore the gas dynamics near the dust sublimation radius of active galactic nucleus (AGN). For the purpose, we perform axisymmetric radiation hydrodynamic simulations of a dusty gas disc of radius 1 pc around a supermassive black hole of mass 10 7 M taking into account (1) anisotropic radiation of accretion disc, (2) X-ray heating by corona, (3) radiative transfer of infrared (IR) photons re-emitted by dust, (4) frequency dependence of direct and IR radiations, and (5) separate temperatures for gas and dust. As a result, we find that for Eddington ratio 0.77, a nearly neutral, dense ( ${\approx } 10^{6{\text{--}}8}\;\mathrm{cm^{-3}}$ ), geometrically thin ( h / r 〈 0.06) disc forms with a high-velocity (200 ~ 3000 km s –1 ) dusty outflow launched from the disc surface. The disc temperature is determined by the balance between X-ray heating and various cooling, and the disc is almost supported by thermal pressure. Contrary to Krolik ( 2007 ), the radiation pressure by IR photons is not effective to thicken the disc, but rather compresses it. Thus, it seems difficult for a radiation-supported, geometrically thick, obscuring torus to form near the dust sublimation radius as far as the Eddington ratio is high (~1). The mass outflow rate is $0.05{\text{--}}0.1\;\mathrm{M}_{\odot }\,\mathrm{yr}^{-1}$ and the column density of the outflow is N H 10 21 cm –2 . To explain observed type-II AGN fraction, it is required that outflow gas is extended to larger radii ( r 10 pc) or that a denser dusty wind is launched from smaller radii ( r ~ 10 4 R g ).
Print ISSN:
0035-8711
Electronic ISSN:
1365-2966
Topics:
Physics
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