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.
This is a pre-copy-editing, author-produced PDF of an article accepted for publication in Monthly Notices of the Royal Astronomical Society following peer review. The definitive publisher-authenticated version J. S. Dunlop, P. A. R. Ade, J. J. Bock, E. L. Chapin, M. Cirasuolo, K. E. K. Coppin, M. J. Devlin, M. Griffin, T. R. Greve, J. O. Gundersen, M. Halpern, P. C. Hargrave, D. H. Hughes, R. J. Ivison, J. Klein, A. Kovacs, G. Marsden, P. Mauskopf, C. B. Netterfield, L. Olmi, E. Pascale, G. Patanchon, M. Rex, D. Scott, C. Semisch, I. Smail, T. A. Targett, N. Thomas, M. D. P. Truch, C. Tucker, G. S. Tucker, M. P. Viero, F. Walter, J. L. Wardlow, A. Weiss, D. V. Wiebe; The BLAST 250 μm-selected galaxy population in GOODS-South, Monthly Notices of the Royal Astronomical Society, Volume 408, Issue 4, 11 November 2010, Pages 2022–2050, https://doi.org/10.1111/j.1365-2966.2010.17278.x is available online at: https://academic.oup.com/mnras/article/408/4/2022/1417321