Magnetic fields and strong density waves in the interacting galaxy NGC 3627

We present 10.55 GHz observations of the strong-density-wave spiral NGC 362 7. Total power and polarization maps with a resolution of 1.'13, sensitive to a weak extended emission were obtained. In the analysis we used also ava ilable data in the CO and H alpha lines. The total power brightness distrib ution shows two equally bright sources close to the bar ends, coincident wi th similar peaks in CO and H alpha. The strong central peak of the CO emission does not correspond to a detecta ble central source in radio continuum. A weak H alpha flux from this region is thus due not only to a strong absorption but may also indicate a low st ar formation level in the central molecular complex. The equally strong tot al power peaks at the bar ends do not reflect the asymmetry of the H alpha emission, the latter being stronger at the northern bar end. The H alpha as ymmetry is likely to be due to differences in absorption. The polarized emission has the form of two asymmetric lobes with B-vectors running parallel to the optical arms. The stronger lobe is located at the p osition of the dust lane in the western arm while the weaker one falls on t he middle of the interarm space in the NE disk. Smooth polarized emission a way from any spiral structures was also detected. Despite the strong densit y waves, many polarization properties of this galaxy like the large-scale d istribution of polarized intensity or azimuthal variations of magnetic pitc h angles can be reasonably explained by the presence of an axisymmetric, dy namo-type magnetic field component. However, extra effects like the depolar ization of the southern segment of the eastern arm by vertical fields above star-forming regions, as well as some compressional enhancement of regular fields in the western arm seem necessary to explain our polarization data.