The SCUBA-2 Cosmology Legacy Survey: 850um maps, catalogues and number counts

Journal article

We present a catalogue of ∼3,000 submillimetre sources detected (≥3.5σ) at 850μm over ∼5 deg2 surveyed as part of the James Clerk Maxwell Telescope (JCMT) SCUBA-2 Cosmology Legacy Survey (S2CLS). This is the largest survey of its kind at 850μm, increasing the sample size of 850-μm-selected submillimetre galaxies by an order of magnitude. The wide 850μm survey component of S2CLS covers the extragalactic fields: UKIDSS-UDS, COSMOS, Akari-NEP, Extended Groth Strip, Lockman Hole North, SSA22 and GOODS-North. The average 1σ depth of S2CLS is 1.2 mJy beam−1, approaching the SCUBA-2 850μm confusion limit, which we determine to be σc ≈ 0.8 mJy beam−1. We measure the 850μm number counts, reducing the Poisson errors on the differential counts to approximately 4% at S850 ≈ 3 mJy. With several independent fields, we investigate field-to-field variance, finding that the number counts on 0.5–1° scales are generally within 50% of the S2CLS mean for S850 > 3 mJy, with scatter consistent with the Poisson and estimated cosmic variance uncertainties, although there is a marginal (2σ) density enhancement in GOODS-North. The observed counts are in reasonable agreement with recent phenomenological and semi-analytic models, although determining the shape of the faint end slope (S850 < 3 mJy) remains a key test. The large solid angle of S2CLS allows us to measure the bright-end counts: at S850 > 10 mJy there are approximately ten sources per square degree, and we detect the distinctive up-turn in the number counts indicative of the detection of local sources of 850μm emission, and strongly lensed high-redshift galaxies. All calibrated maps and the catalogue are made publicly available.

Authors: Geach, J; Dunlop, J; Halpern, M; Smail, I; Werf, P

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: Oxford University Press
• Journal: Monthly Notices of the Royal Astronomical Society
• Volume: 465
• Issue: 2
• Pages: 1789-1806
• Publication date: 2016-11-10
• Acceptance date: 2016-10-19
• DOI: 10.1093/mnras/stw2721
• ISSN: 1365-2966 and 0035-8711
• Keywords: astro-ph.GA; astro-ph.CO; surveys; cosmology: observations; galaxies: high-redshift; catalogues; galaxies: evolution