Extended radio sources and elliptical galaxies. V - Optical positions for 40 identified sources

Abstract

Optical positions generally accurate to about 0.4 arcsec are given for the centers of 40 radio galaxies; the positions have been obtained by the method described in Goodson et al., 1979. Small-diameter radio cores in extended radio structures coincide with 18 of these galaxy centers, so the identifications of the extended structures with these galaxies are essentially unambiguous. The distribution of angular offsets of the radio cores from the centroids of the extended structures are examined for all such unambiguous identifications. The distribution confirms the result of Bridle and Fomalont (1978) that more than 90% of the identifications of clearly bifurcated radio structures are within 0.15 (LAS) of their radio centroids. The reliability of the optical identification is examined for the 22 extended sources in this group which do not have detectable radio cores.