THE OPTICAL POLARIZATION OF THE LOW-REDSHIFT RADIO GALAXIES 3CR-33, 3CR-305, 3CR-321 AND 3CR-459

Polarization maps of a sample of spatially resolved low-z radio galaxies show that there are two components to the polarization. One component is intrinsic to the nucleus, while the other is restricted to elongated or fan-like areas which are centred on the nucleus and are cospatial with the known, extended emission-line regions. The orientation of the nuclear polarization is at large angles to the orientation of the extended polarization and approximately parallel to the main extended structures seen on our polarized intensity maps. These results can be explained in terms of a simple scattering model, although we cannot completely rule out contributions from other mechanisms, such as dichroic extinction by aligned dust grains. The scattering model implies that significant amounts of radiation are escaping at large angles to the radio axis. Thus, in the context of the unified schemes for radio sources, the 'radiation cones' must be broad.