STELLAR MASSES AND STAR FORMATION RATES FOR 1 M GALAXIES FROM SDSS+ WISE

Abstract

We combine SDSS and WISE photometry for the full SDSS spectroscopic galaxy sample, creating SEDs that cover lambda=0.4-22 micron for an unprecedented large and comprehensive sample of 858,365 present-epoch galaxies. Using MAGPHYS we then model simultaneously and consistently both the attenuated stellar SED and the dust emission at 12 micron and 22 micron, producing robust new calibrations for monochromatic mid-IR star formation rate proxies. These modeling results provide the first mid-IR-based view of the bi-modality in star formation activity among galaxies, exhibiting the sequence of star-forming galaxies (main sequence) with a slope of dlogSFR/dlogM*=0.80 and a scatter of 0.39 dex. We find that these new star-formation rates along the SF main sequence are systematically lower by a factor of 1.4 than those derived from optical spectroscopy. We show that for most present-day galaxies the 0.4-22 micron SED fits can exquisitely predict the fluxes measured by Herschel at much longer wavelengths. Our analysis also illustrates that the majorities of stars in the present-day universe is formed in luminous galaxies (~L*) in and around the green valley of the color-luminosity plane. We make the matched photometry catalog and SED modeling results publicly available.