SUBMILLIMETER OBSERVATIONS OF MILLIMETER BRIGHT GALAXIES DISCOVERED BY THE SOUTH POLE TELESCOPE

Abstract

We present APEX SABOCA 350micron and LABOCA 870micron observations of 11\nrepresentative examples of the rare, extremely bright (S_1.4mm > 15mJy),\ndust-dominated millimeter-selected galaxies recently discovered by the South\nPole Telescope (SPT). All 11 sources are robustly detected with LABOCA with 40\n< S_870micron < 130mJy, approximately an order of magnitude higher than the\ncanonical submillimeter galaxy (SMG) population. Six of the sources are also\ndetected by SABOCA at >3sigma, with the detections or upper limits providing a\nkey constraint on the shape of the spectral energy distribution (SED) near its\npeak. We model the SEDs of these galaxies using a simple modified blackbody and\nperform the same analysis on samples of SMGs of known redshift from the\nliterature. These calibration samples inform the distribution of dust\ntemperature for similar SMG populations, and this dust temperature prior allows\nus to derive photometric redshift estimates and far infrared luminosities for\nthe sources. We find a median redshift of <z> = 3.0, higher than the <z> = 2.2\ninferred for the normal SMG population. We also derive the apparent size of the\nsources from the temperature and apparent luminosity, finding them to appear\nlarger than our unlensed calibration sample, which supports the idea that these\nsources are gravitationally magnified by massive structures along the line of\nsight.\n