A two-temperature model for the infrared and radio emission from late-type galaxies

Abstract

The tight correlation between FIR and nonthermal radio luminosities for late-type galaxies is now well established. Using data from the IRAS Point Source Catalog and the 6C radio survey at 151 MHz, it is shown that this correlation is well-fitted by a power law with an index, gamma = 0.86 + or - 0.03, which is consistent with other published FIR/radio correlations. This result is interpreted in the light of proposals that far-infrared emission is due partly to recently formed massive stars and partly to an order population of stars. By means of a simple model, this latter component is removed from the FIR fluxes and the remaining emission is found to be consistent with gamma = 0.97 + or - 0.06, a result which is only weakly dependent on the model parameters. This strongly supports the hypothesis that disk radio emission is related to the formation rate of massive stars, and not to the old stellar population.