The percentage of stellar light re-radiated by dust in late-type Virgo Cluster galaxies

We show that the mean percentage of stellar light re-radiated by dust is ∼30 per cent for the Virgo Cluster late-spirals measured with ISOPHOT by Tuffs et al. A strong dependence of this ratio with morphological type was found, ranging from typical values of ∼15 per cent for early spirals to up to ∼50 per cent for some late spirals. The extreme BCDs can have even higher percentages of their bolometric output re-radiated in the thermal infrared. Luminosity correction factors for the cold dust component are given for general use in converting far-infrared (FIR) luminosities derived from IRAS.