A cloud model of active galactic nuclei: the iron K alpha line diagnostics

The origin and the profile of the iron K alpha line from active galactic nu clei are studied. The model with a quasi-spherical distribution of clouds a round a compact galactic nucleus is explored, in which the intrinsic spectr al feature around 6-7 keV is substantially affected by Comptonization of pr imary X-rays. The predicted spectral profiles are influenced mainly by the motion of the clouds in the strong gravitational field of the centre, and b y the orientation of the source with respect to the observer. The case of t he Seyfert galaxy MCG-6-30-15 is examined in more detail and free: paramete rs of the model are determined, A robust result is obtained: acceptable fit s to the observed profile correspond to a spherical distribution of the clo uds with strong self-obscuration effects and with a rather high value of io nization parameter. This is a different situation from that considered in t he model of a cold illuminated disc, Nevertheless, geometrically flat (disc -type) configurations are not rejected.