Testing the AGN Accretion Disk Paradigm by New SelfConsistent, NonLTE Models
Abstract
We present selfconsistent models of the vertical structure and emergent spectrum of an accretion disk around a supermassive Kerr black hole. For the radial structure, we take into account general relativistic corrections after Riffert & Herold (1996). For computing the vertical structure, the interaction of radiation and matter is treated selfconsistently, taking into account departures from LTE for calculating both the disk structure and the radiation field. We demonstrate that nonLTE effects and the effects of selfconsistent vertical structure of a disk play a very important role in determining the emergent radiation. In particular, nonLTE models exhibit a largely diminished H I Lyman discontinuity when compared to LTE models. Moreover, the He II discontinuity appears strongly in emission for nonLTE models. Consequently, the number of ionizing photons in the He II Lyman continuum increases significantly for nonLTE disk models. This prediction may be important for constraining models of the intergalactic radiation field and the ionization of helium in the intergalactic medium. We also compare the vertical structure models of a disk ring with the nonLTE stellar atmosphere models computed for the same effective temperature and as close surface gravity as possible. We found that athough the predicted flux roughly mimicks the results of selfconsistent calculations, using stellar atmosphere models for approximating the AGN disk emergent radiation is risky because the predicted flux in the vicinity of the H I and He II Lyman discontinuities is very sensitive to the assumed value of the surface gravity.
 Publication:

American Astronomical Society Meeting Abstracts #190
 Pub Date:
 May 1997
 Bibcode:
 1997AAS...190.3910H