Extended optical line emission associated with radio galaxies

A search for optical line emission associated with the jets and lobes of radio galaxies is being conducted with the aid of a video camera and a high gain video spectrometer. Several sources have been found in which extended optical line emission is clearly related to the nonthermal radio emission. The obtained optical imaging and spectroscopic data combined with accurate VLA maps of comparable resolution allow some preliminary, general conclusions to be drawn. The optical line emission is predominantly found along the radio source boundaries. The optical line emission is usually brightest near, but slightly offset from, bright radio knots or hotspots. Generally the radio source is nearly entirely depolarized at 6 cm at locations where the optical line emission overlaps with that of the radio source. Attention is given to the origin of the line emitting gas, the excitation mechanisms, the depolarization mechanisms, and questions concerning the powering of the radio sources.