Upper left panel: radio continuum image at 843 MHz (contours) superimposed on the DSSR image (grayscale). Contours levels go from 4 mJy beam^-1 (~3 rms)to 12 mJy beam^-1 in steps of 4 mJy beam^-1, and from 20 mJy beam^-1 in steps of 10 mJy beam^-1. Upper right panel: radio continuum image at 4800 MHz (contours) superimposed to the DSSR image (grayscale). Contours levels go from 2.4 mJy beam^-1 (~3 rms)to 10.4 mJy beam^-1 in steps of 2 mJy beam^-1, and from 10.4 mJy beam^-1 in steps of 4 mJy beam^-1. The symmetry axis of the nebula is depicted by the dotted line. Lower left panel: radio continuum image at 8640 MHz (contours) superimposed to the DSSR image (grayscale). Contours levels go from 15 mJy beam^-1 (~3 rms)in steps of 1 mJy beam^-1. Lower right panel: emission measure profile obtained from the 4800 MHz radio continuum image along the symmetry axis of NGC 3503 .