Fitting Improved Accretion Disk Models to the Multiwavelength Continua of Quasars and Active Galactic Nuclei

Abstract

We present fits to the ultraviolet-optical-infrared spectra of 60 quasars and active galactic nuclei (AGNs) using improved black hole accretion disk models. The disk is assumed geometrically thin and optically thick. We included the relativistic effects of disk inclination, including Doppler boosting, gravitational focusing, and gravitational redshift, on the observed disk spectra for both Kerr (rotating) and Schwarzschild (nonrotating) black holes. The apparent disk spectrum becomes harder when the disk is viewed at higher inclination angles due to the Doppler boosting and the focusing effects. These relativistic corrections are much more significant in the Kerr geometry since the inner edge of the disk is much closer to the rotating black hole. A simple inverse relation was found between the inferred black hole mass and the assumed inclination angle in the Kerr case, while the inferred accretion rate (M_sun_ yr^-1^) remains independent of the angle. In the Schwarzschild case, however, the ratio of the inferred accretion rate to the black hole mass (M^dot^/M) remains roughly constant when the viewing angle changes. In both geometries, low-redshift Seyfert galaxies have relatively low accretion rates, only a few percent of their Eddington luminosities (L_EDD_), while the most luminous quasars are accreting near their Eddington limits.