Far-infrared properties of Spitzer-selected luminous starbursts

Abstract

We present SHARC-2 350μm data on 20 luminous z ∼ 2 starbursts with S 1.2 mm > 2mJy from the Spitzer-selected samples of Lonsdale etal. and Fiolet etal. All the sources were detected, with S 350 μm > 25mJy for 18 of them. With the data, we determine precise dust temperatures and luminosities for these galaxies using both single-temperature fits and models with power-law mass-temperature distributions. We derive appropriate formulae to use when optical depths are non-negligible. Our models provide an excellent fit to the 6 μm-2mm measurements of local starbursts. We find characteristic single-component temperatures T 1 ≃ 35.5 ± 2.2K and integrated infrared (IR) luminosities around 10 12.9 ± 0.1 L ⊙ for the SWIRE-selected sources. Molecular gas masses are estimated at ≃4 × 1010 M ⊙, assuming κ850 μm = 0.15m 2kg-1 and a submillimeter-selected galaxy (SMG)-like gas-to-dust mass ratio. The best-fit models imply ≳2kpc emission scales. We also note a tight correlation between rest-frame 1.4GHz radio and IR luminosities confirming star formation as the predominant power source. The far-IR properties of our sample are indistinguishable from the purely submillimeter-selected populations from current surveys. We therefore conclude that our original selection criteria, based on mid-IR colors and 24μm flux densities, provides an effective means for the study of SMGs at z ∼ 1.5-2.5. © 2010. The American Astronomical Society.