DETERMINING STAR FORMATION RATES FOR INFRARED GALAXIES

We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 mu m or extinction-corrected Pa alpha luminosities are consistent in the total infrared luminosity = L(TIR) similar to 10(10) L-circle dot range. MIPS 24 mu m photometry can yield SFRs accurately from this luminosity upward: SFR(M-circle dot yr(-1)) = 7.8 x 10(-10) L(24 mu m, L-circle dot) from L(TIR) = 5 x 10(9) L-circle dot to 10(11) L-circle dot and SFR = 7.8 x 10(-10) L(24 mu m, L-circle dot)(7.76 x 10(-11) L(24) )(0.048) for higher L(TIR). For galaxies with L(TIR) >= 10(10) L-circle dot, these new expressions should provide SFRs to within 0.2 dex. For L(TIR) >= 10(11) L-circle dot, we find that the SFR of infrared galaxies is significantly underestimated using extinction-corrected Pa alpha (and presumably using any other optical or near-infrared recombination lines). As a part of this work, we constructed spectral energy distribution templates for eleven luminous and ultraluminous purely star forming infrared galaxies and over the spectral range 0.4 mu m to 30 cm. We use these templates and the SINGS data to construct average templates from 5 mu m to 30 cm for infrared galaxies with L(TIR) = 5 x 10(9) to 10(13) L-circle dot. All of these templates are made available online.