Vertical Structure and Emission Spectrum of an Accretion Disk around a Massive Black Hole

Abstract

Vertical structure and emission spectrum of accretion disks for active galactic nuclei are determined by solving hydrostatic equilibrium and radiative transfer self-consistently for given column density and accretion rate. Numerical calculations are performed for a radial position at 5 times Schwarzschild radius with a black hole mass of 10<SUP>8</SUP> M<SUB>sun</SUB>. The heating rate is assumed to be proportional to the mass density. We found that the emission spectrum deviates from the blackbody spectrum owing to a combined effect of electron scattering and temperature gradient. For a fixed column density corresponding to the total Thomson scattering depth of 1000, the peak of the emission spectrum moves from ultraviolet to soft X-ray range as the accretion rate increases. An inversion in the temperature distribution appears for an accretion rate higher than 10% of the Eddington luminosity. For a lower column density at high accretion rates, we found an optically thin, two-temperature and Comptonized bremsstrahlung dominated but still radiation pressure dominated disk.