Left panel: contribution of the old (red) and young (blue) stellar populations to the unattenuated luminosity, over the bolometric luminosity, per galaxy type and (U)LIRGs merging class. Right panel: contribution of the old and young stellar populations to the attenuated luminosity, over the bolometric luminosity, per galaxy type and (U)LIRGs merging class (same colours as in left panel), together with the ratio of the dust luminosity to the bolometric luminosity (yellow).