Reverberation Mapping and the Disk-Wind Model of the Broad-Line Region

Abstract

Using the disk-wind model of Murray et al., we calculate line profiles and frequency-resolved response functions for broad-line emission from the surface of an accretion disk in an active galactic nucleus in the presence of a radiatively driven wind. We find that the combined effects of the shears in the wind and in the dIsk itself produce anisotropic line emission, which solves several well-known problems connected with disk models of the broad-line region. In particular, the broadening of resonance lines such as C IV, Lyα, and N V can be attributed to orbital motion of the disk gas at radii as close as ~10^16^ cm in Seyferts, without requiring unrealistically large emission regions in order to produce single-peaked profiles. Furthermore, the anisotropy of the line emission results in frequency-dependent response functions which are no longer red-blue symmetric, so that the time delays inferred for the various red and blue components of the line agree qualitatively with recent reverberation mapping observations of NGC 5548.