tokens: of the former ones at higher redshifts. Wang et al. ( 2019 ) reported, for their sample of H-dropout-selected dusty galaxies, a space density (∼2 × 10 −5 Mpc −3 at z > 3) similar to that of our high-redshift UV-dark galaxies, in the same redshift range. However, comparing the two populations, we find that our radio-selected galaxies produce stars at a rate that is on average three times higher. In fact, the median L IR of our galaxies at z > 3 is (6.3 ± 0.5) × 10 12 , which is about three times higher than the median infrared luminosity of (2.2 ± 0.4) × 10 12 reported by Wang et al. for their sample. This means that their contribution to the cosmic SFRD is also higher. In particular, it reaches 7.0 × 10 −3 M ⊙ yr −1 Mpc −3 in the redshift range 3.0 z 4.5, and 5.4 × 10 −3 M ⊙ yr −1 Mpc −3 at 4.5 z 7.7, with uncertainties of the order of 20% (Figure 4 and Table 3 ), therefore doubling the contribution of the population of H-dropouts previously cited at the same cosmic epoch (Wang et al. 2019 ). A similar result was reported for a sample of HST-dark galaxies identified at submillimeter wavelengths in the ALPINE fields Gruppioni et al. ( 2020 ). We compared our own selection criteria also with those by Wang et al. ( 2019 ), again to estimate the possible overlap between the two samples (see the Appendix ), and we concluded that at least ∼82% of the UV-dark radio-selected galaxies are not consistent with the H-dropout selection by Wang et al. ( 2019 ) and therefore constitute a different galaxy population. It is worth noting that we find a similar percentage (83%) when focusing only on the common redshift range between the two samples (z > 3). We compared the trend toward high redshift of the cosmic SFRD of our radio-selected UV-dark galaxies with the estimate based on galaxies identified in the rest-frame UV regime (Madau Dickinson 2014 ; Bouwens et al. 2020 ). 15 15 Bouwens et al. ( 2020 ) include the SFRD contribution from ULIRG-type galaxies in the ASPECS volume, derived from various submillimeter surveys. At 3.0 z 4.5, the contribution of UV-dark radio galaxies to the SFRD corresponds to ∼10-25% of the SFRD of UV-bright galaxies. This fraction rises to ∼25%–40% at z > 4.5, where we identified 22 very-high- z candidates, whose SEDs are illustrated in Figure 5 along with their redshift likelihood distributions. We stress that the actual contribution of radio-selected UV-dark galaxies to the cosmic SFRD could be even higher, because our estimates are derived without any extrapolation to lower fluxes (hence SFRs) than our selection, which would have been extremely uncertain. In fact, the correction for incompleteness, which we apply only takes into account how representative the primary sample is with respect to our total sample of radio-selected UV-dark galaxies. Figure 5. Observed (points as in Figure 1 ) and best-fit (black line) SEDs of the highest-redshift galaxies from our primary subsample (z ≥ 4.5). Error bars are plotted for each data
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