| Summary: | We present Atacama Large Millimeter/submillimeter Array (ALMA) 860 μm imaging of four high-redshift (z = 2.8-5.7) dusty sources that were detected using the South Pole Telescope (SPT) at 1.4 mm and are not seen in existing radio to far-infrared catalogs. At 1."5 resolution, the ALMA data reveal multiple images of each submillimeter source, separated by 1"-3", consistent with strong lensing by intervening galaxies visible in near-IR imaging of these sources. We describe a gravitational lens modeling procedure that operates on the measured visibilities and incorporates self-calibration-like antenna phase corrections as part of the model optimization, which we use to interpret the source structure. Lens models indicate that SPT0346-52, located at z = 5.7, is one of the most luminous and intensely star-forming sources in the universe with a lensing corrected FIR luminosity of 3.7 × 10^(13) L_☉ and star formation surface density of 4200 M_☉ yr^(–1) kpc^(–2). We find magnification factors of 5 to 22, with lens Einstein radii of 1."1-2."0 and Einstein enclosed masses of 1.6-7.2 × 10^(11) M_☉. These observations confirm the lensing origin of these objects, allow us to measure their intrinsic sizes and luminosities, and demonstrate the important role that ALMA will play in the interpretation of lensed submillimeter sources. © 2013 American Astronomical Society. Received 2012 September 18; accepted 2013 March 1; published 2013 April 4. The SPT is supported by the National Science Foundation through grant ANT-0638937, with partial support through PHY-1125897, the Kavli Foundation, and the Gordon and Betty Moore Foundation. This paper makes use of the following ALMA data: ADS/JAO.ALMA #2011.0.00957.S and #2011.0.00958.S. ALMA is a partnership of ESO (representing its member states), NSF (USA) and NINS (Japan), together with NRC (Canada) and NSC and ASIAA (Taiwan), in cooperation with the Republic of Chile. The Joint ALMA Observatory is operated by ESO, AUI/NRAO and NAOJ. The National Radio Astronomy ...
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