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We present high-resolution 870 µm ALMA continuum maps of 30 bright sub-millimeter sources in the UKIDSS UDS field. These sources are selected from deep, 1-degree 2 850-µm maps from the SCUBA-2 Cosmology Legacy Survey, and are representative of the brightest sources in the field (median S SCUBA-2 = 8.7± 0.4 mJy). We detect 52 sub-millimeter galaxies (SMGs) at > 4 σ significance in our 30 ALMA maps. In 61 +19 −15 % 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 L IR > ∼ 10 12 L . The brightest SMG contributes on average 80 +6 −2 % of the single-dish flux density, and in the ALMA maps containing ≥ 2 SMGs the secondary SMG contributes 25 +1 −5 % of the integrated ALMA flux. We construct source counts and show that multiplicity boosts the apparent single-dish cumulative counts by 20 % at S 870 > 7.5 mJy, and by 60 % at S 870 > 12 mJy. We combine our sample with previous ALMA studies of fainter SMGs and show that the counts are well-described by a double powerlaw with a break at 8.5 ± 0.6 mJy. The break corresponds to a luminosity of ∼ 6 × 10 12 L or a star-formation rate of ∼ 10 3 M yr −1 . For the typical sizes of these SMGs, which are resolved in our ALMA data with R e = 1.2 ± 0.1 kpc, this yields a limiting SFR density of ∼100 M yr −1 kpc −2 . Finally, the number density of S 870 > ∼ 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 Herschel Multi-tiered Extragalactic Survey (HerMES) has identified large numbers of dusty star-forming galaxies (DSFGs) over a wide range in redshift. A detailed understanding of these DSFGs is hampered by the limited spatial resolution of Herschel. We present 870 μm 0 45 resolution imaging obtained with the Atacama Large Millimeter/submillimeter Array (ALMA) of a sample of 29 HerMES DSFGs that have far-infrared (FIR) flux densities that lie between the brightest of sources found by Herschel and fainter DSFGs found via groundbased surveys in the submillimeter region. The ALMA imaging reveals that these DSFGs comprise a total of 62 sources (down to the 5s point-source sensitivity limit in our ALMA sample; 0.2 mJy s » ). Optical or nearinfrared imaging indicates that 36 of the ALMA sources experience a significant flux boost from gravitational lensing ( 1.1 m > ), but only six are strongly lensed and show multiple images. We introduce and make use of UVMCMCFIT, a general-purpose and publicly available Markov chain Monte Carlo visibility-plane analysis tool to analyze the source properties. Combined with our previous work on brighter Herschel sources, the lens models presented here tentatively favor intrinsic number counts for DSFGs with a break near 8 mJy at 880 m m and a steep fall-off at higher flux densities. Nearly 70% of the Herschel sources break down into multiple ALMA counterparts, consistent with previous research indicating that the multiplicity rate is high in bright sources discovered in singledish submillimeter or FIR surveys. The ALMA counterparts to our Herschel targets are located significantly closer to each other than ALMA counterparts to sources found in the LABOCA ECDFS Submillimeter Survey. Theoretical models underpredict the excess number of sources with small separations seen in our ALMA sample. The high multiplicity rate and small projected separations between sources seen in our sample argue in favor of interactions and mergers plausibly driving both the prodigious emission from the brightest DSFGs as well as the sharp downturn above S 8 mJy 880 = .

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Take-down policy If you believe that this document breaches copyright please contact us providing details, and we will remove access to the work immediately and investigate your claim.Downloaded from the University of Groningen/UMCG research database (Pure): http://www.rug.nl/research/portal. For technical reasons the number of authors shown on this cover page is limited to 10 maximum. AbstractWe study a large galaxy sample from the Spitzer Matching Survey of the UltraVISTA ultra-deep Stripes (SMUVS) to search for sources with enhanced 3.6 m m fluxes indicative of strong Hα emission at z 3.9 4.9 = -. We find that the percentage of "Hα excess" sources reaches 37%-40% for galaxies with stellar masses M M log 9 10