Left: the 1.4 GHz radio luminosity of supernova remnants (SNRs) detected through forced photometry as a function of the SNR diameter. Right: accurately determined radio spectral indices for the SNRs. The sample has been divided into objects with an X-ray detection plus optical confirmation of high [S II]:Hα ratio (blue), objects with only optical spectroscopic confirmation (orange), objects with only an X-ray detection (green), and objects identified as possible SNRs through optical imaging but without confirmation through spectroscopy or X-ray emission (open circles).