Polarised flux density contours at λ6 cm overlaid on a Hα image from the WIYN Observatory. Contour levels are at 80, 120, 200, 300, 400 μJy beam^-1. In the lower left we show the size of the synthesised beam (12.̋5 × 11.̋7). The red vectors indicate the measured polarised flux density (1″ = 40 μJy beam^-1) and the intrinsic magnetic field direction of the emission. The green cross marks the optical centre of M 82 and the blue ellipse the extent of the central optical disk.