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.