Optical emission in the radio lobes of radio galaxies. II. New observations of 21 radio lobes

We report new identifications of optical emission associated with the radio lobes of double radio galaxies. In addition to optical emission reported earlier, optical emission is present in the outer radio structure of the sources 3C 219, 3C 244.1, 3C 247, 3C 252, 3C 268.2, 3C 321, 3C 319, 3C 337, and possibly in 3C 330. We have not found emission to our detection limit of Vapprox.24 in the sources 3C 79, 3C 173.1, 3C 223, 3C 325, and 3C 381. Of the 21 separate sources in optical studies of extended lobes of radiogalaxies reported to date, 16 radio sources observed so far show significant optical emission within one or both lobes, while in 11 of these the optical object is within 2'' of the radio peak. Some patterns may be emerging in the presence or absence of optical emission