AKARI fluxes at 140 μm plotted against IRAS fluxes at 100 μm (upper panel) and AKARI fluxes at 90 μm (lower panel). The sample is divided into three sub-samples according to the diameter d of the galaxies: d < 1′ (dots), 1′ < d < 1.5′ (small circles), and d > 1.5′ (large circles). The data are compared to model predictions from Dale & Helou (2002) for three different values of the α parameter, α = 1.5,2, and 2.5 (dotted, solid, and dashed lines respectively).