The SCUBA-2 Large eXtragalactic Survey: 850μm map, catalogue and the bright-end number counts of the XMM-LSS field

We present 850 mu m imaging of the XMM-LSS field observed for 170 h as part of the James Clerk Maxwell Telescope SCUBA-2 Large eXtragalactic Survey (S2LXS). S2LXS XMM-LSS maps an area of 9deg(2) reaching a moderate depth of 1 sigma?4mJy beam(-1) 1J?4mJy beam(-1?). This is the largest contiguous area of extragalactic sky mapped by James Clerk Maxwell Telescope (JCMT) at 850 mu m to date. The wide area of the S2LXS XMM-LSS survey allows us to probe the ultra-bright (?S-850 mu m?15mJy ), yet rare submillimetre population. We present the S2LXS XMM-LSS catalogue, which comprises 40 sources detected at > 5 sigma significance, with deboosted flux densities in the range of 77-48mJy48mJy?. We robustly measure the bright-end of the 850 mu m number counts at flux densities > 7mJy > 7mJy?, reducing the Poisson errors compared to existing measurements. The S2LXS XMM-LSS observed number counts show the characteristic upturn at bright fluxes, expected to be motivated by local sources of submillimetre emission and high-redshift strongly lensed galaxies. We find that the observed 850 mu m number counts are best reproduced by model predictions that include either strong lensing or source blending from a 15-arcsec beam, indicating that both may make an important contribution to the observed overabundance of bright single dish 850 mu m selected sources. We make the S2LXS XMM-LSS 850 mu m map and > 5 sigma catalogue presented here publicly available.

Automated summary

This study presents 850 mu m imaging of the XMM-LSS field using the James Clerk Maxwell Telescope. It is the largest contiguous area of extragalactic sky mapped by the telescope at this wavelength. The researchers found that strong lensing and source blending may contribute to the observed overabundance of bright 850 mu m selected sources.