A radio optical reference frame. III. Additional radio and optical positions in the southern hemisphere

Radio and optical positions are presented for southern hemisphere extragalactic sources from the Parkes 2.7 GHz survey. Sixty-one sources were observed with Mark III VLBI at 8.4 GHz (X band) between Tidbinbilla, Australia and Hartebeesthoek, South Africa. The results presented are part of the effort to establish a global reference frame of 400 extragalactic radio sources. Radio positions with ∼10 milliarcsec errors have been estimated for 39 sources not previously in our radio reference frame catalog, and provisional positions were obtained for two additional sources, bringing the total number of catalog sources to 276. The principal source of error is the uncalibrated ionosphere. Of the remaining sources five were completely undetected, six were either too faint or too resolved, and nine had previous catalog positions. Optical positions on the FK5 system have also been measured for four southern sources using prime focus plates from the Anglo-Australian 4 m telescope with an accuracy 0.″06. This raises to 40 the number of radio sources with accurately measured positions for their optical counterparts.