Far-Infrared Properties of Spitzer-selected Luminous Starbursts

TL;DR

This study analyzes the far-infrared properties of 20 luminous starburst galaxies at z~2, revealing their dust temperatures, luminosities, and gas masses, and confirming the effectiveness of mid-IR selection for studying submillimeter galaxies.

Contribution

It provides detailed dust temperature and luminosity measurements for Spitzer-selected starbursts, demonstrating their similarity to submillimeter-selected populations and validating mid-IR selection methods.

Findings

Average dust temperature ~35.5 K

Infrared luminosities around 10^13 Lsun

Gas masses estimated at 4 x 10^10 Msun

Abstract

We present SHARC-2 350 micron data on 20 luminous z ~ 2 starbursts with S(1.2mm) > 2 mJy from the Spitzer-selected samples of Lonsdale et al. and Fiolet et al. All the sources were detected, with S(350um) > 25 mJy 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 6um--2mm measurements of local starbursts. We find characteristic single-component temperatures T1 ~ 35.5+-2.2 K and integrated infrared (IR) luminosities around 10^(12.9+-0.1) Lsun for the SWIRE-selected sources. Molecular gas masses are estimated at 4 x 10^(10) Msun, assuming kappa(850um)=0.15 m^2/kg and a submillimeter-selected galaxy (SMG)-like gas-to-dust mass ratio. The best-fit models imply >~2 kpc emission scales. We also note a tight correlation between rest-frame 1.4 GHz 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 24 um flux densities, provides an effective means for the study of SMGs at z ~ 1.5--2.5.