A POLARIZATION STUDY OF RADIO GALAXIES AND QUASARS SELECTED FROM THE MOLONGLO COMPLETE SAMPLE

We present total intensity and linear polarization observations made w ith the Very Large Array at lambda lambda 20 and 6 cm of a representat ive sample of 42 radio galaxies and quasars selected from the Molonglo complete sample. The sources have been chosen to be of large size to probe the depolarizing medium on these scales using our present data a nd later with observations at lower frequencies with the Giant Metrewa ve Radio Telescope. The lambda lambda 20 and 6 cm data are of similar resolutions and show that depolarization between these two wavelengths is seen largely only in those lobes which are within about 300 kpc of the parent galaxy. Examination of the depolarization of the lobes wit h ann-length asymmetry shows that depolarization is observed predomina ntly for the lobe which is closer to the nucleus. There is also a tren d for the lobe closer to the nucleus to be brighter, consistent with t he scenario that the nearer lobe is interacting with a denser environm ent which is responsible for the higher depolarization and greater dis sipation of energy. We have also examined the depolarization asymmetry of die lobes on opposite sides of the nucleus for galaxies and quasar s, This shows that the depolarization asymmetry for quasars is margina lly higher than that for galaxies. The depolarization properties of ou r sample are possibly determined by an asymmetric environment as well as the effects of orientation.