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Description
We present deep 450{mu}m and 850{mu}m observations of a large, uniformly covered 394arcmin^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_=4.13mJy and {sigma}_850_=0.80mJy. The differential and cumulative number counts are presented and compared to similar previous works. Individual point sources are identified at >3.6{sigma} significance, a threshold corresponding to a 3-5% sample contamination rate. We identify 78 sources at 450{mu}m and 99 at 850{mu}m, with flux densities S_450_=13-37mJy and S_850_=2-16mJy. Only 62-76% of 450{mu}m sources are 850{mu}m detected and 61-81% 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% of 450{mu}m sources and 60% of 850{mu}m sources have 24{mu}m or radio counterparts. 450{mu}m selected galaxies peak at <z>=1.95+/-0.19 and 850{mu}m selected galaxies peak at <z>=2.16+/-0.11. The two samples occupy similar parameter space in redshift and luminosity, while their median SED peak wavelengths differ by ~20-50{mu}m (translating to {Delta}T_dust_=8-12K, 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 (>~30%) at censusing infrared-luminous star formation at high z.
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