THE STRUCTURE OF SOUTHERN EXTRAGALACTIC RADIO-SOURCES

We report the structure of extragalactic radio sources south of declination -30' that have been imaged with the Molonglo Observatory Synthesis Telescope (MOST) at 843 MHz with a resolution of 44'. Our sample includes those sources noted in the Molonglo Reference Catalogue (MRC) as extended (larger than approximately 1'), as well as those noted as multiple-that is, within 8' of a neighbor and possibly related. The sample is representative of the strong extended extragalactic radio sources of the southern sky, but is not statistically complete. We observed 339 sources with either time-shared or full 12 hr aperture-synthesis observations. The results are given as radio images and a table of flux densities, positions and, sizes for 383 sources, Most of the groups of multiple sources are found to be separate, unrelated sources, as expected, but some are components of larger sources. Some of the sources flagged as extended in the MRC are also groups of unrelated sources, confused in the MRC beam. After excluding such random associations we then determine a confirmed MRC extended sample of 193 sources with flux density greater than 0.4 Jy (at 843 MHz) and size greater than 0'5. The selection effects and completeness for this sample are discussed. The UK Schmidt southern sky survey was used to make I 1 7 new optical identifications, and to reexamine previous identifications. The positions and IIIaJ magnitudes are presented for all sources that now have an identification, together with their redshifts when known. We present new redshifts for 14 galaxies from observations with the Anglo-Australian Telescope.