The magnetic field structure in NGC 253 in presence of a galactic wind

We present radio continuum polarimetry observations of the nearby edge-on galaxy NGC 253 which possesses a very bright radio halo. Using the vertical synchrotron emission proles and the lifetimes of cosmic-ray electrons, we determined the cosmic-ray bulk speed as 300 30 km s 1 , indicating the presence of a galactic wind in this galaxy. The large-scale mag- netic eld was decomposed into a toroidal axisymmetric component in the disk and a poloidal component in the halo. The poloidal component shows a prominent X-shaped magnetic eld