A Glimpse of the New Redshift Frontier through AS1063

Abstract We report the discovery of two galaxy candidates at redshifts between 15.7 − 3.4 7 − 0.10 + 0.13 at M UV = −17, is in clear tension with pre-JWST theoretical predictions, extending the overabundance of galaxies from z ∼ 10 to z ∼ 17. These results, together with the scarcity of brighter galaxies in other public surveys, suggest a steep decline in the bright end of the UV luminosity function at z ∼ 16, implying efficient star formation and possibly a close connection to the halo mass function at these redshifts. Testing a variety of star formation histories suggests that these sources are plausible progenitors of the unusually UV-bright galaxies that JWST now routinely uncovers at z = 10–14. Overall, our results indicate that the luminosity distribution of the earliest star-forming galaxies could be shifting toward fainter luminosities, implying that future surveys of cosmic dawn will need to explore this faint luminosity regime.