Abstract
We present and analyze the correlations between mid-infrared (MIR), far-infrared (FIR), total-infrared (TIR), Hα, and far-UV (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 Hα, TIR, and FUV luminosities, and we rescaled the MIR-derived SFR formulae according to the above correlations with differences less than 15%. We confirm the recent result by Calzetti and coworkers that the combined observed -->H α + 24 μm luminosities -->L(H αobs + 24 μm) possess very tight correlation with the extinction-corrected Hα luminosities L(Hαcorr) for star-forming and even for dwarf galaxies, and show that the combined -->L(H αobs + 8 μm [dust]) are also tightly correlated with L(Hαcorr) for the above sample galaxies. Among all the L(MIR)-L(FIR) correlations for star-forming galaxies, the L(24 μm) versus L(70 μm) and L(8 μm[dust]) versus L(160 μm) 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-Hα/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.
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