Calibration of the total infrared luminosity of nearby galaxies from Spitzer and Herschel bands

Abstract

We present new empirical calibrations to estimate resolved and integrated\ntotal infrared luminosities from Spitzer and Herschel bands used as\nmonochromatic or combined tracers. We base our calibrations on resolved\nelements of nearby galaxies (3 to 30 Mpc) observed with Herschel. We perform a\nresolved SED modelling of these objects using the Draine and Li (2007) dust\nmodels and investigate the influence of the addition of SPIRE measurements in\nthe estimation of LTIR. We find that using data up to 250 um leads to local\nLTIR values consistent with those obtained with a complete coverage (up to 500\num) within 10 per cent for most of our resolved elements. We then study the\ndistribution of energy in the resolved SEDs of our galaxies. The bulk of energy\n(30-50 per cent) is contained in the (70-160 um) band. The (24-70 um) fraction\ndecreases with increasing metallicity. The (160-1100 um) submillimeter band can\naccount for up to 25 per cent of the LTIR in metal-rich galaxies. We\ninvestigate the correlation between TIR surface brightnesses/luminosities and\nmonochromatic Spitzer and Herschel surface brightnesses/luminosities. The three\nPACS bands can be used as reliable monochromatic estimators of the LTIR, the\n100 um band being the most reliable monochromatic tracer. There is also a\nstrong correlation between the SPIRE 250um and LTIR, although with more scatter\nthan for the PACS relations. We also study the ability of our monochromatic\nrelations to reproduce integrated LTIR of nearby galaxies as well as LTIR of\nz=1-3 sources. Finally, we provide calibration coefficients that can be used to\nderive TIR surface brightnesses/luminosities from a combination of Spitzer and\nHerschel surface brightnesses/fluxes and analyse the associated uncertainties.\n