On the Observational Evidence for Accretion Disks in Active Galactic Nuclei

We show that the double-peaked emission lines observed in the active galaxy 3C 390.3 cannot be produced by two line-emitting streams (generated by a two-sided jet). The reason for this is that, as we show, the emitting region on the receding jet is obscured from view by the accretion disk, leaving the accretion disk as the only viable site for the production of these lines.