A general relativistic study of the infrared emission from massive black holes in the nuclei of active galaxies

Abstract

The possibility that some portion of the infrared (IR) radiation emanating from Active Galactic Nuclei (AGN's) may arise from disklike structures of ionized plasma accreting onto massive or supermassive black holes motivates the investigation of the effects on the observed radiation of the strong gravitational fields in the vicinity of the emitting particles. Numerous previous studies have been incomplete in several respects: (a) they have neglected to take into account the contribution to the observed specific power flux of radiation emitted from the underside of the disk and gravitationally lensed into the upper half-hemisphere; (b) they have considered only a limited range of observing positions and hole spins; (c) many have been restricted to examination of the steady state flux arising from homogeneous disks; (d) they have employed a methodology not readily extendible to the analysis of gravitational effects on radiation arising from more complicated physical systems (e.g., nonplanar ensembles of gaseous clouds). The present study develops, within the context of the optically thick, geometrically thin accretion disk model, a new method of complementary images. Fully taking into account the so-called first-orbit disk images, including the effects of disk self-occlusion, for the entire range of observing positions and hole spins, and for both homogeneous and thermally inhomogeneous disks, it applies this method to both steady state and time-dependent analyses in the paradigm case of the Galactic Center black hole candidate Sagittarius A*. Completely general results applicable to any similar black hole-accretion disk system are presented. An illustration is given of how the basic method, along with ancillary analytical devices such as that of extended images and computationally efficient techniques based on their properties, may be extended to the analysis of considerably more complicated physical systems, and tentative results for the case of the Broad Line Region (BLR) of quasar spectra are presented.