Radio continuum observations of the spiral galaxies NGC 2841, NGC 5055, and NGC 7331

The radio continuum emission of the nearby spiral galaxies NGC 2841, 5055, and 7331 has been mapped with the Westerbork Synthesis Radio Telescope at wavelengths of 50 and 21 cm. The radio continuum emission is distributed similarly to the light distribution but is not as flattened as the neutral hydrogen distribution. The spectral index distribution shows a general steepening of the radio spectrum toward the edge of the galaxies. This cannot be explained by the influence of the thermal emission alone but requires energy losses of the relativistic electrons which diffuse in both the radial and the Z direction.