OPTICAL POLARIZATION AND MAGNETIC-FIELDS IN SPIRAL GALAXIES

Optical polarization maps are presented for a selection of galaxies wi th quite different morphologies. Those galaxies seen at small angles o f inclination so that their spiral structure can be seen show large-sc ale spiral patterns of polarization orientations which follow the arm and interarm structure. The galaxies viewed close to edge-on, where th e obscuration forms a central bisecting dust lane, also have large-sca le patterns of polarization orientations but with the vectors parallel to the dust lane axis in the central regions and perpendicular to the axis at the extremities. The interpretation of these results is discu ssed in terms of relating the observed optical polarization data to th e large-scale magnetic fields in galaxies.