Structure of line-emitting accretion disks in active galactic nuclei - ARP 102B

We present a self-consistent model of a line-emitting accretion disk which accounts for the observed properties of a small class of AGNs. The prime objects are Arp 102B and 3C 390. 3, broad-line radio galaxies with double-peaked emission lines which have been attributed to a Keplerian disk. Historical objections to locating the broad emission-line region in the accretion disks of AGNs generally involve the energy budget of the disk itself and the inability of the disk to subtend a large enough solid angle at the central source for photoionization to be effective. If, however, the inner disk is a thick, hot ion torus which illuminates a thin outer disk with ionizing radiation, then the flux intercepted by the thin disk and its variation of emissivity with radius are in agreement with the observed line fluxes and with detailed fits to the double-peaked profiles. Improved calculations of the line profile of a relativistic, Keplerian disk, generalized to include a variety of emissivity laws as well as local broadening due to electron scattering or turbulence, fit Arp 102B very well. Analytic and numerical calculations of the solid angle presented by the outer, thin disk to an extended, isotropic source of illumination, demonstrate that the energy budget requirements for line emission from the disk are also satisfied. The theory of hot ion tori was originally motivated by the need to explain the jets in radio galaxies, which apparently have low accretion luminosity. The combination of ion torus/thin disk accounts for several additional properties of Arp 102B and 3C 390. 3. The far-infrared peaks at 25 micron are in agreement with the predicted synchrotron self-absorption turnover for an ion torus. The outer radius of the hot ion torus, which is identified with the measured inner radius of the line-emitting thin disk, is consistent with the theoretical location of the onset of the Lightman-Eardley instability. Observed broadening of the Balmer lines is probably due to electron scattering in the photoionized atmosphere of the thin disk, where T <= 10⁵^ K.