Correlations between IR Luminosity, Star Formation Rate, and CO Luminosity in the Local Universe

We exploit the DustPedia sample of galaxies within approximately 40 Mpc, selecting 388 sources, to investigate the correlations between IR luminosity (LIR), the star formation rate (SFR), and the CO(1-0) luminosity (LCO) down to much lower luminosities than reached by previous analyses. We find a sub-linear dependence of the SFR on LIR. Below log(LIR/L⊙)≃10 or SFR≃1M⊙yr−1, the SFR/LIR ratio substantially exceeds the standard ratio for dust-enshrouded star formation, and the difference increases with decreasing LIR values. This implies that the effect of unobscured star formation overcomes that of dust heating by old stars, at variance with results based on the Planck ERCSC galaxy sample. We also find that the relations between the LCO and LIR or the SFR are consistent with those obtained at much higher luminosities.