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Department of Physics

# Staff profile

## Publication details for Professor Ian Smail

Simpson, J.M., Smail, I., Swinbank, A.M., Ivison, R.J., Dunlop, J.S., Geach, J.E., Almaini, O., Arumugam, V., Bremer, M.N., Chen, C.-C., Conselice, C., Coppin, K.E.K., Farrah, D., Ibar, E., Hartley, W.G., Ma, C.J., Michałowski, M.J., Scott, D., Spaans, M., Thomson, A.P. & van der Werf, P.P. (2017). The SCUBA-2 Cosmology Legacy Survey: Multi-wavelength Properties of ALMA-identified Submillimeter Galaxies in UKIDSS UDS. The Astrophysical Journal 839(1): 58.

### 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.