The SCUBA-2 Cosmology Legacy Survey: galaxies in the deep 850 μm survey, and the star-forming 'main sequence'

We investigate the properties of the galaxies selected from the deepest 850-mu m survey undertaken to date with (Submillimetre Common-User Bolometer Array 2) SCUBA-2 on the James Clerk Maxwell Telescope as part of the SCUBA-2 Cosmology Legacy Survey. A total of 106 sources (>5 sigma) were uncovered at 850 mu m from an area of similar or equal to 150 arcmin(2) in the centre of the COSMOS/UltraVISTA/Cosmic Assembly Near-infrared Deep Extragalactic Legacy Survey (CANDELS) field, imaged to a typical depth of sigma(850) similar or equal to 0.25 mJy. We utilize the available multifrequency data to identify galaxy counterparts for 80 of these sources (75 per cent), and to establish the complete redshift distribution for this sample, yielding (z) over bar = 2.38 +/- 0.09. We have also been able to determine the stellar masses of the majority of the galaxy identifications, enabling us to explore their location on the star formation rate: stellar mass (SFR:M*) plane. Crucially, our new deep 850-mu m-selected sample reaches flux densities equivalent to SFR similar or equal to 100 M-circle dot yr(-1), enabling us to confirm that sub-mm galaxies form the high-mass end of the 'main sequence' (MS) of star-forming galaxies at z > 1.5 (with a mean specific SFR of sSFR = 2.25 +/- 0.19 Gyr(-1) at z similar or equal to 2.5). Our results are consistent with no significant flattening of the MS towards high masses at these redshifts. However, our results add to the growing evidence that average sSFR rises only slowly at high redshift, resulting in log(10)sSFR being an apparently simple linear function of the age of the Universe.