abstract
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The first deep blank-field 450um map (1-sigma~1.3mJy) from the SCUBA-2
Cosmology Legacy Survey (S2CLS), conducted with the James Clerk Maxwell
Telescope (JCMT) is presented. Our map covers 140 arcmin^2 of the COSMOS field,
in the footprint of the HST CANDELS area. Using 60 submillimetre galaxies
(SMGs) detected at >3.75-sigma, we evaluate the number counts of 450um-selected
galaxies with flux densities S_450>5mJy. The 8-arcsec JCMT beam and high
sensitivity of SCUBA-2 now make it possible to directly resolve a larger
fraction of the cosmic infrared background (CIB, peaking at ~200um) into the
individual galaxies responsible for its emission than has previously been
possible at this wavelength. At S_450>5mJy we resolve (7.4[+/-]0.7)x10^-2
MJy/sr of the CIB at 450um (equivalent to 16[+/-]7% of the absolute brightness
measured by COBE at this wavelength) into point sources. A further ~40% of the
CIB can be recovered through a statistical stack of 24um emitters in this
field, indicating that the majority (~60%) of the CIB at 450um is emitted by
galaxies with S_450>2mJy. The average redshift of 450um emitters identified
with an optical/near-infrared counterpart is estimated to be
=1.3, implying that the galaxies in the sample are in the ultraluminous class (L_IR~1.1x10^12 L_sun). If the galaxies contributing to the statistical stack lie at similar redshifts, then the majority of the CIB at 450um is emitted by galaxies in the LIRG class with L_IR>3.6x10^11 L_sun.