Evolutionary stage and extended radio structures of active galactic nuclei.

Radio galaxies with broad emission lines (broad-line radio galaxies) in the optical spectra and extended radio structures have a distribution with respect to the linear dimensions of these structures that is very different from the corresponding distribution for the majority of radio galaxies. The form of the distribution indicates that galaxies with broad lines exhibit a stage in activity of the nucleus that occurs, not at the beginning, but nearer the end of the existence of the extended radio structure. The subclass of quasars with extended radio structures have on the average a low optical luminosity, a large amplitude of optical variability, and very broad lines in the optical spectra and evidently relate to the same stage of activity.