Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy Survey

We present a new exploration of the cosmic star formation history and dust obscuration in massive galaxies at redshifts 0.5 < z < 6. We utilize the deepest 450-and 850-mu m imaging from SCUBA-2 CLS, covering 230 arcmin(2) in the AEGIS, COSMOS and UDS fields, together with 100-250 mu m imaging from Herschel. We demonstrate the capability of the T-PHOT deconfusion code to reach below the confusion limit, using multiwavelength prior catalogues from CANDELS/3D-HST. By combining IR and UV data, we measure the relationship between total star formation rate (SFR) and stellar mass up to z similar to 5, indicating that UV-derived dust corrections underestimate the SFR in massive galaxies. We investigate the relationship between obscuration and the UV slope (the IRX-beta relation) in our sample, which is similar to that of low-redshift starburst galaxies, although it deviates at high stellar masses. Our data provide new measurements of the total SFR density (SFRD) in M-* > 10(10) M-O galaxies at 0.5 < z < 6. This is dominated by obscured star formation by a factor of > 10. One third of this is accounted for by 450 mu m-detected sources, while one-fifth is attributed to UV-luminous sources (brighter than L-UV(*)), although even these are largely obscured. By extrapolating our results to include all stellar masses, we estimate a total SFRD that is in good agreement with previous results from IR and UV data at z <= 3, and from UV-only data at z similar to 5. The cosmic star formation history undergoes a transition at z similar to 3-4, as predominantly unobscured growth in the early Universe is overtaken by obscured star formation, driven by the build-up of the most massive galaxies during the peak of cosmic assembly.