Extended Data Fig. 4: Fraction of obscured star-formation as a function of stellar mass.

The fraction of obscured star-formation, \({f}_{{\rm{obs}}}={{\rm{SFR}}}_{{\rm{IR}}}/({{\rm{SFR}}}_{{\rm{IR}}}+{{\rm{SFR}}}_{{\rm{UV}}})\), of REBELS-29-2 and REBELS-12-2 (dark coloured squares) is significantly higher than for typical LBGs at their stellar mass. The line shows the observed, constant relation between z ≈ 0 and z ≈ 2.5 (ref. ⁶³) assuming a given set of SED templates from Bethermin and colleagues⁶⁵. Blue and brown small points with error bars show stacked results of star-forming galaxies at z ≈ 4.5 and at z ≈ 5.5, respectively⁶⁴. The star-formation of extreme starburst galaxies at z ≈ 5.7–6.9 is essentially 100% obscured (SMGs;¹² green small points). The highly obscured star-forming galaxies found as companions of high-redshift quasars at z > 6 (refs. ^13,14) (yellow diamonds) are substantially more massive than the galaxies identified here, as estimated from their dynamical masses. Squares show the obscured fraction of our UV-bright and dusty galaxies. Error bars correspond to 1σ uncertainty, and arrows show 2σ lower/upper limits. Our discovery of lower mass, obscured galaxies shows that f_obs is likely to vary much more strongly at a fixed stellar mass than previously estimated even in the epoch of reionization.