Submillimeter Observations of Distant Red Galaxies: Uncovering the 1mjy 850μm-population

We present a study of the submillimeter (submm) 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 submm image of a field centred on the cluster MS 1054−03, we obtain a statistical detection of the DRGs at redshift z = 2 − 3.5, with an average 850μm flux density of 1.11 ± 0.28mJy. The detection implies an average star formation rate (SFR) of 127 ± 34M⊙ 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 submm agrees well with SFRs derived from SED fitting of optical-near-infrared data and average Xray emission. Constant Star Formation models imply ages of 2Gyr, extinction AV = 2.4mag, 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 respectively to the submm background. Simple estimates suggest that these populations contribute ∼ 50% of the flux from sources with 0.5 < f850 < 5mJy, which is where the peak of energy is produced. We have therefore uncovered one of the most important populations of galaxies contributing to the sub-mm background. Subject headings: Galaxies: high-redshift — galaxies: evolution — submillimeter