University of Hertfordshire

From the same journal

From the same journal

By the same authors


  • J. M. Simpson
  • Ian Smail
  • A. M. Swinbank
  • R. J. Ivison
  • J. S. Dunlop
  • J. E. Geach
  • O. Almaini
  • V. Arumugam
  • M. N. Bremer
  • Chian-Chou Chen
  • C. Conselice
  • K. E. K. Coppin
  • D. Farrah
  • E. Ibar
  • W. G. Hartley
  • C. J. Ma
  • M. J. Michalowski
  • M. Spaans
  • A. P. Thomson
  • P. P. van der Werf
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Original languageEnglish
Number of pages16
JournalThe Astrophysical Journal
Publication statusPublished - 13 Apr 2017


We present a multi-wavelength analysis of 52 sub-millimeter galaxies (SMGs), identified using ALMA 870$\mu$m continuum imaging in a pilot program to precisely locate bright SCUBA2-selected sub-mm sources in the UKIDSS Ultra Deep Survey (UDS) field. Using the available deep (especially near-infrared), panoramic imaging of the UDS field at optical-to-radio wavelengths we characterize key properties of the SMG population. The median photometric redshift of the bright ALMA/SCUBA-2 UDS (AS2UDS) SMGs that are detected in a sufficient number of wavebands to derive a robust photometric redshift is $z$=2.65$\pm$0.13. However, similar to previous studies, 27% of the SMGs are too faint at optical-to-near-infrared wavelengths to derive a reliable photometric redshift. Assuming that these SMGs lie at z$\gtrsim$3 raises the median redshift of the full sample to $z$=2.9$\pm$0.2. A subset of 23, unlensed, bright AS2UDS SMGs have sizes measured from resolved imaging of their rest-frame far-infrared emission. We show that the extent and luminosity of the far-infrared emission are consistent with the dust emission arising from regions that are optically thick, on average, at a wavelength of $\lambda_0$$\ge$75$\mu$m (1-$\sigma$ dispersion of 55-90$\mu$m). Using the dust masses derived from our optically-thick spectral energy distribution models we determine that these galaxies have a median hydrogen column density of $N_{H}$=9.8$_{-0.7}^{+1.4}$$\times$10$^{23}$cm$^{-2}$, or a corresponding median $V$-band obscuration of $A_\mathrm{v}$=540$^{+80}_{-40}$mag, averaged along the line of sight to the source of their restframe $\sim$200$\mu$m emission. We discuss the implications of this extreme attenuation by dust for the multiwavelength study of dusty starbursts and reddening-sensitive tracers of star formation.


The Astrophysical Journal, 839:58 (16pp), 2017 April, doi: © 2017. The American Astronomical Society. All rights reserved.

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