Data in Tables 3 and 4 plotted as spectral luminosity vs diameter in log–log scale. The surface brightness detection limit of BB335B is shown as a dashed line, and the fitted luminosity completeness limit L_c, as derived in Sect. 3.4, is shown as a dotted line. The lower panel show 45 SNRs in M 82 plotted as black crosses (data from Huang et al. 1994, their Table 2, scaled to 6 cm assuming α = −0.5). The evolution of SN1986J during its first 30 years is plotted as a solid curve, from the model described in Sect. 3.1.