Characterization of Scuba-2 450 mu m and 850 mu m selected galaxies in the COSMOS field

International audienceWe present deep 450 mu m and 850 mu m observations of a large, uniformly covered 394 arcmin(2) area in the Cosmic Evolution Survey (COSMOS) field obtained with the Scuba-2 instrument on the James Clerk Maxwell Telescope (JCMT). We achieve root-mean-square noise values of Sigma(450) = 4.13 mJy and Sigma(850) = 0.80 mJy. The differential and cumulative number counts are presented and compared to similar previous works. Individual point sources are identified at \textgreater 3.6 Sigma significance, a threshold corresponding to a 3-5 per cent sample contamination rate. We identify 78 sources at 450 mu m and 99 at 850 mu m, with flux densities S-450 = 13-37 mJy and S-850 = 2-16 mJy. Only 62-76 per cent of 450 mu m sources are 850 mu m detected and 61-81 per cent of 850 mu m sources are 450 mu m detected. The positional uncertainties at 450 mu m are small (1-2.5 arcsec) and therefore allow a precise identification of multiwavelength counterparts without reliance on detection at 24 mu m or radio wavelengths; we find that only 44 per cent of 450 mu m sources and 60 per cent of 850 mu m sources have 24 mu m or radio counterparts. 450 mu m selected galaxies peak at \textless\textless z \textgreater\textgreater = 1.95 +/- 0.19 and 850 mu m selected galaxies peak at \textless\textless z \textgreater\textgreater = 2.16 +/- 0.11. The two samples occupy similar parameter space in redshift and luminosity, while their median SED peak wavelengths differ by similar to 20-50 mu m (translating to delta T-dust = 8-12 K, where 450 mu m selected galaxies are warmer). The similarities of the 450 mu m and 850 mu m populations, yet lack of direct overlap between them, suggests that submillimetre surveys conducted at any single far-infrared wavelength will be significantly incomplete (greater than or similar to 30 per cent) at censusing infrared-luminous star formation at high z