Extended Data Fig. 3: Probing a new parameter space of DSFGs.

a, The stellar mass as a function of redshift for DSFGs from the literature. IRAC-selected, H-dropout galaxies (light-grey dots with 1σ errorbars¹⁵) are generally more massive than the two serendipitously detected REBELS galaxies (red dots). Additionally, the redshifts of H-dropouts are extremely uncertain (photo-z). The extremely star-bursting SMG population only shows a small tail of rare sources at z > 4 (shown by dark dots¹¹). The blue squares show all the previously known DSFGs at z > 5.5 with spectroscopically measured redshifts, while purple squares correspond to z ≈ 6 QSO companion galaxies¹³. These are more extreme sources than REBELS-12-2 and REBELS-29-2. b, The infrared luminosity/SFR_IR as a function of redshift for the same galaxy samples as on the left. The infrared luminosities and hence SFRs of the newly identified galaxies are substantially lower than typical SMGs at these redshifts. For both panels, error bars correspond to 1σ uncertainties, and arrows show 2σ upper/lower limits.