Strong magnetic asymmetries in weakly interacting spirals

We investigate the influence of cluster environment on the structure and evolution of magnetic fields and the interstellar medium in the Virgo cluster spiral NGC 4254. Our sensitive interferometric (VLA) and single dish (Effelsberg) radio polarimetric observations reveal several magnetic spiral arms displaced from optical ones. However, the southern arm, particularly bright in polarized emission, lacks an optical counterpart. In this area the magnetic pitch angle is very small. On the contrary, the northern part of the galaxy with more diffuse total radio emission shows a significant radial component of the magnetic field. At 1.4 GHz the galaxy shows an extended polarized envelope with a highly regular magnetic field extending further than any star-forming region. The regular component enters the cluster environment and can enrich the cluster-scale magnetic field. Our XMM-Newton observations reveal that the broadband X-ray emission of the hot gas emerges from almost the whole galaxy disk and is tightly associated with regions of star formation. The distribution of X-rays does not show any sign of stripped hot gas around the galaxy disk and rules out strong ram pressure of the hot cluster gas. Magnetic asymmetries and slightly perturbed H I and optical emission probably manifest weak tidal interactions of NGC 4254 with other Virgo cluster members: the dark galaxy VIRGOHI 21 or NGC 4262. We also compare polarimetric properties of NGC 4254 with other Virgo cluster spirals which we currently observe systematically with the Effelsberg radio telescope.