Red, redder, reddest: SCUBA-2 imaging of colour-selected Herschel sources

S. Duivenvoorden, S. Oliver, J. M. Scudder, J. Greenslade, D. A. Riechers, S. M. Wilkins, V. Buat, S. C. Chapman, D. L. Clements, A. Cooray, K. E. K. Coppin, H. Dannerbauer, G. De Zotti, J. S. Dunlop, S. A. Eales, A. Efstathiou, D. Farrah, J. E. Geach, W. S. Holland, P. D. HurleyR. J. Ivison, L. Marchetti, G. Petitpas, M. T. Sargent, D. Scott, M. Symeonidis, M. Vaccari, J. D. Vieira, L. Wang, J. Wardlow, M. Zemcov

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High-redshift, luminous, dusty star-forming galaxies (DSFGs) constrain the extremity of galaxy formation theories. The most extreme are discovered through follow-up on candidates in large area surveys. Here, we present extensive 850 μm SCUBA-2 follow-up observations of 188 red DSFG candidates from the Herschel Multitiered Extragalactic Survey (HerMES) LargeMode Survey, covering 274 deg 2.We detected 87 per cent with a signal-to-noise ratio > 3 at 850 μm. We introduce a new method for incorporating the confusion noise in our spectral energy distribution fitting by sampling correlated flux density fluctuations from a confusion limited map. The new 850 μm data provide a better constraint on the photometric redshifts of the candidates, with photometric redshift errors decreasing from σ z/(1 + z) ≈ 0.21 to 0.15. Comparison spectroscopic redshifts also found little bias (〈(z-z spec)/(1+z spec)〉 = 0.08). The mean photometric redshift is found to be 3.6 with a dispersion of 0.4 and we identify 21 DSFGs with a high probability of lying at z > 4. After simulating our selection effects we find number counts are consistent with phenomenological galaxy evolution models. There is a statistically significant excess of WISE-1 and SDSS sources near our red galaxies, giving a strong indication that lensing may explain some of the apparently extreme objects. Nevertheless, our sample includes examples of galaxies with the highest star formation rates in the Universe (≫10 3 M yr -1).

Original languageEnglish
Article numbersty691
Pages (from-to)1099–1119
Number of pages21
JournalMonthly Notices of the Royal Astronomical Society
Issue number1
Early online date15 Mar 2018
Publication statusPublished - 11 Jun 2018


  • Galaxies: High-redshift
  • Galaxies: Starburst
  • Infrared: Galaxies
  • Submillimetre: Galaxies


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