Characterisation of SCUBA-2 450um and 850um-selected Galaxies in the
  COSMOS Field
  We present deep 450um and 850um observations of a large, uniformly covered
394arcmin^2 area in the COSMOS field obtained with the SCUBA-2 instrument on
the James Clerk Maxwell Telescope (JCMT). We achieve root-mean-square noise
values of 4.13mJy at 450um and 0.80mJy at 850um. The differential and
cumulative number counts are presented and compared to similar previous works.
Individual point sources are identified at >3.6sigma significance, a threshold
corresponding to a 3-5% sample contamination rate. We identify 78 sources at
450um and 99 at 850um, with flux densities S450=13-37mJy and S850=2-16mJy. Only
62-76% of 450um sources are 850um detected and 61-81% of 850um sources are
450um detected. The positional uncertainties at 450um are small (1-2.5") and
therefore allow a precise identification of multiwavelength counterparts
without reliance on detection at 24um or radio wavelengths; we find that only
44% of 450um-selected galaxies and 60% of 850um-sources have 24um or radio
counterparts. 450um-selected galaxies peak at <z>=1.95+-0.19 and 850um=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
~10-50um (translating to deltaTdust =8-12K, where 450um-selected galaxies are
warmer). The similarities of the 450um and 850um populations, yet lack of
direct overlap between them, suggests that submillimeter surveys conducted at
any single far-infrared wavelength will be significantly incomplete (~>30%) at
censusing infrared-luminous star formation at high-z.
