S/N maps at 850 μm. The position of the brighter (fainter) quasar is indicated by a black (brown) star. Identified catalog SMGs are marked by black circles with the same size as the effective beam FWHM of 14.6″. The gray dashed line indicates the edge of the effective area (2.5 × the central rms). Sources inconsistent with the expected SMG SED at the quasar redshift are marked with gray rectangles.