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 850μm imaging from SCUBA-2 CLS, covering 230arcmin2 in the AEGIS, COSMOS and UDS fields, together with 100-250μm imaging from Herschel. We demonstrate the capability of the T-PHOT deconfusion code to reach below the confusion limit, using multi-wavelength 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∼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-β 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∗>1010M⊙ 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 450μm-detected sources, while one fifth is attributed to UV-luminous sources (brighter than LUV∗), 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∼5. The cosmic star-formation history undergoes a transition at z∼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.

astro-ph.GA, astro-ph.IM