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Published June 11, 2013 | Published
Journal Article Open

The SCUBA-2 Cosmology Legacy Survey: blank-field number counts of 450-μm-selected galaxies and their contribution to the cosmic infrared background

Abstract

The first deep blank-field 450 μm map (1σ ≈ 1.3 mJy) from the Submillimetre Common-User Bolometer Array-2 SCUBA-2 Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell Telescope (JCMT) is presented. Our map covers 140 arcmin^2 of the Cosmological Evolution Survey field, in the footprint of the Hubble Space Telescope (HST) Cosmic Assembly Near-Infrared Deep Extragalactic Legacy Survey. Using 60 submillimetre galaxies detected at ≥3.75σ, we evaluate the number counts of 450-μm-selected galaxies with flux densities S_450 > 5 mJy. The 8 arcsec JCMT beam and high sensitivity of SCUBA-2 now make it possible to directly resolve a larger fraction of the cosmic infrared background (CIB, peaking at λ ∼ 200 μm) into the individual galaxies responsible for its emission than has previously been possible at this wavelength. At S_450 > 5 mJy, we resolve (7.4 ± 0.7) × 10^(−2) MJy sr^(−1) of the CIB at 450 μm (equivalent to 16 ± 7 per cent of the absolute brightness measured by the Cosmic Background Explorer at this wavelength) into point sources. A further ∼40 per cent of the CIB can be recovered through a statistical stack of 24 μm emitters in this field, indicating that the majority (≈60 per cent) of the CIB at 450 μm is emitted by galaxies with S_450 > 2 mJy. The average redshift of 450 μm emitters identified with an optical/near-infrared counterpart is estimated to be 〈z〉 = 1.3, implying that the galaxies in the sample are in the ultraluminous class (L_IR ≈ 1.1 × 10^(12) L_⊙). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450 μm is emitted by galaxies in the luminous infrared galaxy (LIRG) class with LIR > 3.6 × 10^(11)  L_⊙.

Additional Information

© 2013 The Authors. Published by Oxford University Press on behalf of the Royal Astronomical Society. Accepted 2013 February 22. Received 2013 February 7; in original form 2012 November 28. First published online: April 19, 2013. JEG is supported by a Banting Fellowship, administered by NSERC. JSD acknowledges the support of the European Research Council via the award of an Advanced Grant, and the support of the Royal Society via a Wolfson Research Merit award. MM and IGR acknowledge the support of STFC. The authors thank M. Béthermin for providing data on the 500 μm stacking and parametric model, and J. Dempsey for advice on the SCUBA-2 calibration. It is also a pleasure to thank the JCMT telescope operators J. Hoge, J. Wouterloot and W. Montgomerie, without whom these observations would not be possible. The JCMT is operated by the Joint Astronomy Centre on behalf of the Science and Technology Facilities Council of the United Kingdom, the Netherlands Organisation for Scientific Research and the National Research Council of Canada. Additional funds for the construction of SCUBA-2 were provided by the Canada Foundation for Innovation. Herschel is an ESA space observatory with science instruments provided by European-led Principal Investigator consortia and with important participation from NASA. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA.

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August 22, 2023
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October 24, 2023