SPITZER OBSERVATIONS OF COLD DUST GALAXIES

We combine new Spitzer Space Telescope observations in the mid-infrared and far-infrared ( FIR) with SCUBA 850 mu m observations to improve the measurement of dust temperatures, masses, and luminosities for 11 galaxies of the SCUBA Local Universe Galaxy Survey. By fitting dust models we measure typical dust masses of 10(7.9) M(circle dot) and dust luminosities of similar to 10(10) L(circle dot), for galaxies with modest star formation rates. The data presented in this paper combined with previous observations show that cold dust is present in all types of spiral galaxies and is a major contributor to their total luminosity. Because of the lower dust temperature of the SCUBA sources measured in this paper, they have flatter FIR nu F(nu)(160 mu m)/nu F(nu)(850 mu m) slopes than the larger Spitzer Infrared Nearby Galaxies Survey (SINGS), the sample that provides the best measurements of the dust properties of galaxies in the nearby universe. The new data presented here added to SINGS extend the parameter space that is well covered by local galaxies, providing a comprehensive set of templates that can be used to interpret the observations of nearby and distant galaxies.