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Session 39 - AGNs, QSOs, Active Galaxies.
Display session, Wednesday, June 11
South Main Hall,
We present self-consistent 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 amp; Herold (1996). For computing the vertical structure, the interaction of radiation and matter is treated self-consistently, taking into account departures from LTE for calculating both the disk structure and the radiation field.
We demonstrate that non-LTE effects and the effects of self-consistent vertical structure of a disk play a very important role in determining the emergent radiation. In particular, non-LTE models exhibit a largely diminished H I Lyman discontinuity when compared to LTE models. Moreover, the He II discontinuity appears strongly in emission for non-LTE models. Consequently, the number of ionizing photons in the He II Lyman continuum increases significantly for non-LTE 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 non-LTE 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 self-consistent 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.
