Four left panels: histograms showing the values of the coefficient that multiply the IR luminosity, a_IR, in the hybrid tracers using bins of morphological types. Early-type, star-forming galaxies, considered here as S0/a, Sa, and Sab, are shown in red, intermediate-type spirals such as Sb and Sbc appear in gray, and Sc-Sd-Sm-Irr galaxies are represented in blue. Vertical dashed lines correspond to the median value of each galaxy group. Black top marks show the median value for all the galaxies as in Fig. 16. There is a clear trend with the morphological type, late-type galaxies need a higher value of the a_IR coefficient than early-type galaxies. This trend could be explained in terms of the contribution of an obscured AGN, a missing fraction of the Hα extinction-corrected SFR, or heating by optical photons. Four right panels: same histograms as before, except removing the type-2 AGN. There is still a trend with the morphological type, although it is less obvious that in the previous case.