Evolution of cosmic star formation in the SCUBA-2 Cosmology Legacy Survey
Scott, D.; Dunlop, J. S.; Farrah, D.; Castellano, M.; Santini, P.; Merlin, E.; Fontana, A.; Michałowski, M. J.; Halpern, M.; Knudsen, K. K.; Simpson, J. M.; van der Werf, P. P.; Conselice, C. J.; Shu, X. W.; Geach, J. E.; Bourne, N.; Schreiber, C.; Coppin, K. E. K.; Mortlock, A.; Smith, D. J. B.; Simpson, C.; Parsa, S.
United Kingdom, Italy, Netherlands, United States, Canada, Sweden, China
Abstract
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-μm imaging from SCUBA-2 CLS, covering 230 arcmin2 in the AEGIS, COSMOS and UDS fields, together with 100-250 μm 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 ∼ 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_{\ast }>10^{10} M_{⊙} 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-μm-detected sources, while one-fifth is attributed to UV-luminous sources (brighter than L_UV^\ast), 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.