We present high-resolution 870 μm Atacama Large Millimeter/sub-millimeter Array (ALMA) continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1 degree2 850 μm maps from the SCUBA-2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median 
= 8.7 ± 0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at >4σ significance in our 30 ALMA maps. In 
of the ALMA maps the single-dish source comprises a blend of ≥2 SMGs, where the secondary SMGs are Ultra-luminous Infrared Galaxies (ULIRGs) with 
1012 
. The brightest SMG contributes on average 
of the single-dish flux density, and in the ALMA maps containing ≥2 SMGs the secondary SMG contributes 
of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20% at S870 > 7.5 mJy, and by 60% at S870 > 12 mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double power law with a break at 8.5 ± 0.6 mJy. The break corresponds to a luminosity of ~6 × 1012 
or a star formation rate (SFR) of ~103 
. For the typical sizes of these SMGs, which are resolved in our ALMA data with 
= 1.2 ± 0.1 kpc, this yields a limiting SFR density of ~100 
yr−1 kpc−2 Finally, the number density of S870 
2 mJy SMGs is 80 ± 30 times higher than that derived from blank-field counts. An over-abundance of faint SMGs is inconsistent with line-of-sight projections dominating multiplicity in the brightest SMGs, and indicates that a significant proportion of these high-redshift ULIRGs are likely to be physically associated.
The full paper can be found in Simpson et al. 2015, ApJ, 807, 128
ALMA 870 μm continuum maps, at 0farcs8 resolution, of 30 bright sub-mm sources in the UDS field. These sources are selected to be representative of the brightest sources detected in the S2CLS survey of this ~0.8 deg2 field. The × 18” non-primary-beam-corrected maps (roughly 150 kpc × 150 kpc at the typical SMG redshift, z = 2.5) are ordered by decreasing single-dish flux density and have a median 1-σ rms of 0.26 mJy beam−1. The dashed circle on each thumbnail represents the primary beam (FWHM) of ALMA at 870 μm. We detect 52 SMGs at >4σ (marked by a squares) in the 30 ALMA maps, with 870 μm flux densities of 1.3–12.9 mJy. In 18/30 ALMA maps the single-dish sub-mm source fragments into two or more individual SMGs. In particular, we highlight UDS 57, 168, 286 and 306, where the ALMA observations demonstrate that the single-dish source is comprised of three-or-four SMGs. In two ALMA maps, UDS 252 and 421, we do not detect any SMGs, but note that both SCUBA-2 sources are detected in Herschel/SPIRE imaging. We plot contours representing the single-dish SCUBA-2 emission at 3, 3.5, 4.0, for these sources, note that UDS 421 has a potential VLA/1.4 GHz counterpart (diamond; Arumugan et al. submitted) that is not detected in our ALMA maps.