On the radial dependence of the disk FeKα line emissivity in active galactic nuclei

The iron K alpha fluorescent line detected in many Seyfert 1 galaxies by ASCA and BeppoSAX is usually considered to arise in the innermost region of an accretion disk around a supermassive black hole. The line profile is usually modelled by assuming that the disk emissivity follows a power law, epsilon(R)proportional to R-q. We present a new technique to invert the line profile and infer: (a) the free-format epsilon(R), (b) the disk inclination to the line of sight and (c) the black hole angular momentum. The application of this technique to published K alpha data shows that the line shapes are consistent with the accretion disk model and that the major contribution to the emissivity comes from the innermost disk regions. We also show that a sharp distinction between different black hole angular momenta can usually not be made on the basis of present data. (C) 2000 Elsevier Science B.V. All rights reserved.