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Simpson, J.M. and Smail, Ian and Swinbank, A.M. and Ivison, R.J. and Dunlop, J.S. and Geach, J.E. and Almaini, Omar and Arumugam, Vinodiran and Bremer, M.N. and Chen, Chian-Chou and Conselice, Christopher J. and Coppin, K.E.K. and Farrah, D. and Ibar, E. and Hartley, W.G. and Ma, C.J. and Michałowski, M.J. and Scott, D. and Spaans, M. and Thomson, A.P. and Werf, P. van der (2017) The SCUBA-2 Cosmology Legacy Survey: multi-wavelength properties of ALMA-identified submillimeter galaxies in UKIDSS UDS. Astrophysical Journal, 839 (1). 58/1-58/16. ISSN 1538-4357

Abstract

We present a multi-wavelength analysis of 52 submillimeter galaxies (SMGs), identified using ALMA 870 μm continuum imaging in a pilot program to precisely locate bright SCUBA-2-selected submillimeter 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 ± 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 gsim 3 raises the median redshift of the full sample to z = 2.9 ± 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, on average, optically thick at a wavelength of ${\lambda }_{0}\geqslant 75\,\mu {\rm{m}}$ (1σ dispersion of 55–90 μm). 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${}_{-0.7}^{+1.4}$ × 1023 cm−2, or a corresponding median V-band obscuration of A v = 540${}_{-40}^{+80}$ mag, averaged along the line of sight to the source of their rest-frame ~200 μm emission. We discuss the implications of this extreme attenuation by dust for the multi-wavelength study of dusty starbursts and reddening-sensitive tracers of star formation.

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