Faint Submillimeter Galaxies Identified through Their Optical/Near-infrared Colors. I. Spatial Clustering and Halo Masses

Abstract

The properties of submillimeter galaxies (SMGs) that are fainter than the confusion limit of blank-field single-dish surveys (S850≲ 2 mJy) are poorly constrained. Using a newly developed color selection technique, Optical-Infrared Triple Color (OIRTC), that has been shown to successfully {select} such faint SMGs, we identify a sample of 2938 OIRTC-selected galaxies, dubbed Triple Color Galaxies (TCGs), in the UKIDSS-UDS field. We show that these galaxies have a median 850 μm flux of S850=0.96±0.04 mJy (equivalent to a star-formation rate SFR ∼60−100 M⊙ yr−1 based on SED fitting), representing the first large sample of faint SMGs that bridges the gap between bright SMGs and normal star-forming galaxies in S850 and LIR. We assess the basic properties of TCGs and their relationship with other galaxy populations at z∼2. We measure the two-point autocorrelation function for this population and derive a typical halo mass of log10(Mhalo) =12.9+0.2−0.3, 12.7+0.1−0.2, and 12.9+0.2−0.3 h−1M⊙ at z=1−2, 2−3, and 3−5, respectively. Together with the bright SMGs (S850≳2 mJy) and a comparison sample of less far-infrared luminous star-forming galaxies, we find a lack of dependence between spatial clustering and S850 (or SFR), suggesting that the difference between these populations may lie in their local galactic environment. Lastly, on the scale of ∼8−17 kpc at 1