The magnetic field in the perturbed spiral galaxy NGC 4254

The results of a deep total power and polarization study of the perturbed Virgo Cluster spiral NGC 4254 in radio continuum at 10.55 GHz are presented. The galaxy is found to possess a bright radio disk with some asymmetries similar to those in the H I line and probably attributed to external interactions. The polarized intensity exhibits a U-shaped structure around the disk of NGC 4254 with a strong maximum at the southern disk boundary and a deep minimum on the northern disk region, both probably related to external interactions. There is no obvious association of the polarized brightness distribution with the optical spiral pattern. Close to the optical arms the polarization vectors are aligned with them (with local deviations). However, they continue to form a very regular structure between the arms and in regions of chaotic optical structures, too. A detailed modeling shows that the polarization cannot originate only in compression regions associated with spiral arms. The polarization properties of NGC 4254 can be much better explained by assuming an axisymmetric dynamo field locally modified by spiral arms and external interactions.