Submillimeter Observations of Distant Red Galaxies: Uncovering the 1 mJy 850 μm Population

Abstract

We present a study of the submillimeter emission of distant red galaxies (DRGs). The DRGs are selected by the criterion J - K > 2.3, and are generally massive galaxies at redshifts higher than 2, with red rest-frame optical colors. Using a deep SCUBA submillimeter image of a field centered on the cluster MS 1054-03, we obtain a statistical detection of the DRGs at redshift z = 2-3.5, with an average 850 μm flux density of 1.11 ± 0.28 mJy. The detection implies an average star formation rate (SFR) of 127 ± 34 M ⊙ yr -1 (lensing corrected), assuming that the far-infrared (FIR) spectral energy distribution (SED) is well described by a modified blackbody. The SFR derived from the submillimeter agrees well with SFRs derived from SED fitting of optical-near-infrared data and average X-ray emission. Constant star formation models imply ages of 2 Gyr, extinction A v = 2.4 mag, which is consistent with the FIR to rest-frame optical luminosity ratio of ∼15. DRGs are older and have lower SFRs relative to optical luminosity than (ultra-) luminous infrared galaxies, although their FIR luminosities are similar. The DRGs at 2 < z < 3.5 and the extremely red objects (I - K > 4) at 1 < z < 2, which were also investigated, contribute 5.7 and 5.9 Jy deg -2 , respectively, to the submillimeter background. Simple estimates suggest that these populations contribute ∼50% of the flux from sources with 0.5 < f 850 < 5 mJy, which is where the peak of energy is produced. We have therefore uncovered one of the most important populations of galaxies contributing to the submillimeter background. © 2005. The American Astronomical Society. All rights reserved.