Faint Submillimeter Galaxies identified through their optical/near-infrared colours I: spatial clustering and halo masses

The properties of submillimeter galaxies (SMGs) that are fainter than the confusion limit of blank-field single-dish surveys ($S_{850}\lesssim$ 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 $\mu$m flux of S${}_{850}=0.96\pm 0.04$ mJy (equivalent to a star-formation rate SFR $\sim 60-100$ M${}_{\odot }$ 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 S${}_{850}$ and $L_{\mathrm{I}\mathrm{R}}$. We assess the basic properties of TCGs and their relationship with other galaxy populations at $z\sim 2$. We measure the two-point autocorrelation function for this population and derive a typical halo mass of log${}_{10}$(M${}_{\mathrm{h}\mathrm{a}\mathrm{l}\mathrm{o}}$) $=12.9_{-0.3}^{+0.2}$, $12.7_{-0.2}^{+0.1}$, and $12.9_{-0.3}^{+0.2}$ $h^{-1}$M${}_{\odot }$ at $z=1-2$, $2-3$, and $3-5$, respectively. Together with the bright SMGs (S${}_{850}\gtrsim 2$ mJy) and a comparison sample of less far-infrared luminous star-forming galaxies, we find a lack of dependence between spatial clustering and S${}_{850}$ (or SFR), suggesting that the difference between these populations may lie in their local galactic environment. Lastly, on the scale of $\sim 8-17$ kpc at $1<z<5$ we find a tentative enhancement of the clustering of TCGs over the comparison star-forming galaxies, suggesting that some faint SMGs are physically associated pairs, perhaps reflecting a merging origin in their triggering.