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$_{850} = 0.96\pm0.04$ mJy
(equivalent to a star-formation rate SFR $\sim60-100$ 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
$L_{\rm IR}$. We assess the basic properties of TCGs and their relationship
with other galaxy populations at $z\sim2$. We measure the two-point
autocorrelation function for this population and derive a typical halo mass of
log$_{10}$(M$_{\rm halo}$) $=12.9^{+0.2}_{-0.3}$, $12.7^{+0.1}_{-0.2}$, and
$12.9^{+0.2}_{-0.3}$ $h^{-1}$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 $\sim8-17$ 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.
