Differential Line Development and the Complex Structure of the Broad-Line Region in Fairall 9

Abstract

We find that the profiles of the UV emission lines Lyα, C IV λ1549, and Mg II λ2798, in the Seyfert 1 galaxy Fairall 9 vary such that the lines are broader when the object is brighter. The profile changes occur mainly near the line center for Lyα and C IV and in the wings for Mg II. These results indicate that the broad-line region (BLR) has a complex structure, possibly with nonspherical components. We derive that part of the Lyα and practically all of the C IV emission comes from optically thin clouds in the inner region of the BLR which are heated by an anisotropic UV continuum. These clouds may be moving radially. The Mg II and the rest of the Lyα emission comes from very optically thick clouds which are more spherically distributed at a larger radius and heated mainly by X-ray radiation.