Total non-thermal intensity (in colour) of M 31 at λ6.2 cm smoothed to 3′ HPBW, in coordinates along the major and minor axes of M 31. The rms noise is 0.35 mJy beam⁻¹. The lines show the intrinsic magnetic field orientations at the same resolution, corrected for Faraday rotation measured between λ6.2 cm and λ3.6 cm (see Fig. 22), with lengths proportional to the degree of non-thermal polarization, where the length of a beam width corresponds to 30%. No lines are plotted where PI is below 0.2 mJy beam⁻¹. Polarized background sources have been subtracted. The HPBW is indicated in the bottom left corner.