Correlations between MIR, FIR, H$α$, and FUV Luminosities for SWIRE galaxies

Abstract

e present and analyze the correlations between mid-infrared (MIR), far-infrared (FIR), total-infrared (TIR), H$α$, and FUV luminosities for star-forming galaxies, composite galaxies and AGNs, based on a large sample of galaxies selected from the $Spitzer$ SWIRE fields. The MIR luminosities of star-forming galaxies are well correlated with their H$α$, TIR and FUV luminosities, and we re-scaled the MIR-derived SFR formulae according to the above correlations with differences less than 15%. We confirm the recent result by calzetti et al. (2007) that the combined observed H$α$ + 24$μ$m luminosities L(H$α$$_{\rm obs}$+ 24$μ$m) possess very tight correlation with the extinction-corrected H$α$ luminosities L(H$α$$\_$corr) for star-forming and even for dwarf galaxies, and show that the combined L(H$α$$_{\rm obs}$+ 8$μ$m[dust]) are also tightly correlated with L(H$α$$\_$corr) for the above sample galaxies. Among all the L(MIR)-L(FIR) correlations for star-forming galaxies, the L(24$μ$m) vs. L(70$μ$m) and L(8$μ$m[dust]) vs. L(160$μ$m) are the tightest and also nearly linear. The former could be related to young massive star formation, while the latter might be relevant to diffuse dust emissions heated by old stellar populations. Composite galaxies and AGNs have higher MIR-to-H$α$/MIR-to-FUV luminosity ratios than star-forming galaxies, nevertheless their correlations among MIR, FIR and TIR luminosities are completely following those of star-forming galaxies.