Optical line emission associated with the radio galaxy 4C 26.42 in the cluster of galaxies Abell 1795

Abstract

Extended optical emission-line gas has been detected from the radio galaxy 4C 26.42. A detailed study of the radio and optical emission is presented comprising VLA maps at 20, 6, and 2 cm, broad- and narrow-band optical images, and long-slit spectra. The data show that the (nonthermal) radio continuum and the (thermal) optical line emission in this source are intimately related. X-ray observations have shown that the cluster of galaxies Abell 1795, of which the parent cD galaxy of 4C 26.42 is the dominant member, has a cooling X-ray core centered on the cD galaxy. It is therefore plausible that the line emission in 4C 26.42 is caused by radiatively regulated accretion. Estimates of the Hα surface brightness, and the implied external pressure on the filaments, are consistent with such a model. Slow motion of the cD galaxy relative to the cluster is implied by the data.