Radio – FIR diagram for our Virgo objects plotted as symbols with labels and for the reference sample of galaxies observed by Gioia et al. (1982) with an extension towards low surface-brightness objects observed by Chyży et al. (2006) – both as dots. The surface brightness at 4.85 GHz (Jy/◻′) and at 60 μm (Jy/◻′, see text) is used. The solid curve is an orthogonal fit to reference non-cluster galaxies with a slope of 0.96 ± 0.06. The dashed lines show the “regression scissors”, the maximum and minimum slopes (1.03 and 0.90) allowed by the data scatter.