Polarimetric imaging of interacting pairs
  We present optical polarization maps of a sample of four interacting pairs at different phases of encounter, from nearly unperturbed galaxies to on-going mergers. Only the pair RR 24 shows a linear polarization pattern which extends in both galaxies for several kiloparsecs. The more perturbed member, RR 24b, is lineraly polarized up to the level of ~3%. No polarization is measured in the strongly perturbed late-type pair members of RR 23 and RR 99. Also, in the central part of the double nuclei shell galaxy ESO 2400100 there is no significant polarization. We use the ionized gas velocity field of RR 24 to interpret its linear polarization structure. In RR 24a the quite regular gas kinematics reflect the unperturbed spiral-like polarization structure. In RR 24b a strong velocity gradient in ionized gas could be associated with the polarization structure. We suggest that the large-scale magnetic field of the RR 24 pair members still plays a role in shaping the polarization pattern. 
R. Rampazzo, C. Bonoli, E. Giro