γ-ray luminosity, or the upper limit at 2σ confidence level on the luminosity, of the different sources in the sample and other known high-energy emitting starburst and normal galaxies, given against the supernova rate times the total gas mass in these objects. The red square points show the expectations on the luminosity from the model of Pavlidou & Fields (2001), accounting for the uncertainties on R_SN and M_gas.