X-Ray--heated Coronae and Winds from Accretion Disks: Time-dependent Two-dimensional Hydrodynamics with Adaptive Mesh Refinement

Abstract

We perform first-time time-dependent, 2-D, axisymmetric hydrodynamic simulations using local adaptive mesh refinement of thermally driven rotating winds from X-ray-irradiated accretion disks. The disk is assumed to flare in height with radius allowing direct exposure from the central X-ray source. The heating and cooling are treated strictly in the optically thin approximation. We adopt two spectra characteristic of active galactic nuclei (AGNs) which have Compton temperatures of {ital T}{sub IC}{approx_equal}1.3{times}10{sup 7} K and 10{sup 8} K. We have computed a number of models which cover a large range in luminosity (0.002{le}{ital L}/{ital L}{sub Eddington}{le}1) and radius ({approx_lt}20 Compton radii). Our models extend and improve on the analytic predictions of Begelman, McKee, & Shields (BMS) for Compton-heated winds by including non-Compton processes such as photoionization heating and line cooling, typical of X-ray-heated winds. These non-Compton processes can be dominant at low temperatures ({approx_lt}10{sup 7} K), thus being important in the wind regions of AGNs. Our results agree well with a number of predictions given by BMS, even when non-Compton processes dominate, suggesting that their analytic approximations of the hydrodynamics of disk winds are applicable to the more general area of X-ray-heated winds. In the regime in which Compton processes dominate (i.e.,more » {ital T}{sub IC}=10{sup 8} K spectrum), we have used our results to improve the analytic predictions of BMS, providing a new expression for the mass-loss rate and a modified view of the wind solution topology. We find that beginning from a basically static state, the time-dependent flow which develops eventually settles into a {ital steady} wind, without any evidence of hydrodynamic instabilities. The solution topology consists of a corona with an exponentially truncated wind at small radii, and a vigorous wind at large radii which can be impeded by gravity for small luminosities.« less