Determining Star Formation Rates for Infrared Galaxies
Abstract
We show that measures of star formation rates (SFRs) for infrared galaxies using either single-band 24 um or extinction-corrected Paschen-alpha luminosities are consistent in the total infrared luminosity = L(TIR) ~ 1010 Lsun range. MIPS 24 micron photometry can yield star formation rates accurately from this luminosity upward: SFR(Msun/yr) = 7.8 x 10-10 L(24 um, Lsun) from L(TIR) = 5 x 109 Lsun to 1011 Lsun, and SFR = 7.8 x 10-10 L(24 um, Lsun) x (7.76 x 10-11 L(24))0.048 for higher L(TIR). For galaxies with L(TIR) >= 1010 Lsun, these new expressions should provide SFRs to within 0.2 dex. For L(TIR) >= 1011 Lsun, 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 (SED) templates for eleven luminous and ultraluminous purely star forming infrared galaxies (LIRGs and ULIRGs) and over the spectral range 0.4 microns to 30 cm. We use these templates and the SINGS data to construct average templates from 5 microns to 30 cm for infrared galaxies with L(TIR) = 5 x 109 to 1013 Lsun. All of these templates are made available on line.