Active Galaxies With Double-Peaked Emission Lines and What They Imply About the "Broad-Line Region"

I review the distinguishing observational characteristics of active galaxies with double-peaked emission lines and their implications for the nature of the line-emitting region. Since double-peaked lines most likely originate in the outer parts of the accretion disk, they can be used to study the structure and dynamics of the disk and the associated wind. Such studies lead to general inferences about the broad-line regions of all AGNs. To this end, I describe the results of recent UV spectroscopy of double-peaked emitters that probes the disk-wind relation. I also summarize efforts to exploit the variability of the lines to study dynamical and thermal phenomena in the disk.