A Submillimeter Survey of Faint Galaxies behind 10 Strong Lensing Clusters

We present deep SCUBA-2 450 mu m and 850 mu m imaging of 10 strong lensing clusters. We provide a >4 sigma SCUBA-2 850 mu m catalog of the 404 sources lying within a radius of 4.' 5 4.5 sigma Atacama Large Millimeter/submillimeter Array (ALMA) 850 mu m detections in the clusters A370, MACSJ1149.5+2223, and MACSJ0717.5+3745 from our targeted ALMA observations, along with catalogs of all other >4.5 sigma ALMA (mostly 1.2 mm) detections in any of our cluster fields from archival ALMA observations. For the ALMA detections, we give spectroscopic or photometric redshifts, where available, from our own Keck observations or from the literature. We confirm the use of the 450-850 mu m flux ratio for estimating redshifts. We use lens models to determine magnifications, most of which are in the 1.5-4 range. After supplementing the ALMA cluster sample with Chandra Deep Field ALMA and Submillimeter Array samples, we find no evidence for evolution in the redshift distribution of submillimeter galaxies down to demagnified 850 mu m fluxes of 0.5 mJy. Given this result, we conclude that our observed trend of increasing F160W to 850 mu m flux ratio from brighter to fainter demagnified 850 mu m flux results from the fainter submillimeter galaxies having less extinction. However, there is wide spread in this relation, including the presence of some optical/near-infrared dark galaxies down to fluxes below 1 mJy. Finally, with insights from our ALMA analysis, we analyze our SCUBA-2 sample and present 55 850 mu m bright z > 4 candidates.