Dunlop, J. S. and Ade, P. A. R. and Bock, J. J. and Chapin, E. L. and Cirasuolo, M. and Coppin, K. E. K. and Devlin, M. J. and Griffin, M. and Greve, T. R. and Gundersen, J. O. and Halpern, M. and Hargrave, P. C. and Hughes, D. H. and Ivison, R. J. and Klein, J. and Kovacs, A. and Marsden, G. and Mauskopf, P. and Netterfield, C. B. and Olmi, L. and Pascale, E. and Patanchon, G. and Rex, M. and Scott, D. and Semisch, C. and Smail, I. and Targett, T. A. and Thomas, N. and Truch, M. D. P. and Tucker, C. and Tucker, G. S. and Viero, M. P. and Walter, F. and Wardlow, J. L. and Weiss, A. and Wiebe, D. V. (2010) The BLAST 250 μm-selected galaxy population in GOODS-South. Monthly Notices of the Royal Astronomical Society, 408 (4). pp. 2022-2050. ISSN 0035-8711
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Abstract
We identify and investigate the nature of the 20 brightest 250μm sources detected by the Balloon-borne Large Aperture Submillimetre Telescope (BLAST) within the central 150arcmin2 of the Great Observatories Origins Deep Survey (GOODS)-South field. Aided by the available deep VLA 1.4GHz radio imaging, reaching S1.4 ~= 40μJy (4σ), we have identified radio counterparts for 17/20 of the 250μm sources. The resulting enhanced positional accuracy of ~=1arcsec has then allowed us to exploit the deep optical (Hubble Space Telescope), near-infrared (VLT) and mid-infrared (Spitzer) imaging of GOODS-South to establish secure galaxy counterparts for the 17 radio-identified sources, and plausible galaxy candidates for the three radio-unidentified sources. Confusion is a serious issue for this deep BLAST 250μm survey, due to the large size of the beam. Nevertheless, we argue that our chosen counterparts are significant, and often dominant contributors to the measured BLAST flux densities. For all of these 20 galaxies we have been able to determine spectroscopic (eight) or photometric (12) redshifts. The result is the first near-complete redshift distribution for a deep 250μm-selected galaxy sample. This reveals that 250μm surveys reaching detection limits of ~=40mJy have a median redshift z ~= 1, and contain not only low-redshift spirals/LIRGs, but also the extreme z ~= 2 dust-enshrouded starburst galaxies previously discovered at sub-millimetre wavelengths. Inspection of the LABOCA 870μm imaging of GOODS-South yields detections of ~=1/3 of the proposed BLAST sources (all at z > 1.5), and reveals 250/870μm flux-density ratios consistent with a standard 40K modified blackbody fit with a dust emissivity index β = 1.5. Based on their Infrared Array Camera (IRAC) colours, we find that virtually all of the BLAST galaxy identifications appear better described as analogues of the M82 starburst galaxy, or Sc star-forming discs rather than highly obscured ULIRGs. This is perhaps as expected at low redshift, where the 250μm BLAST selection function is biased towards spectral energy distributions which peak longward of λrest = 100μm. However, it also appears largely true at z ~= 2.