A Glimpse of the New Redshift Frontier through AS1063
Year: 2025
Type: article
Abstract: We report the discovery of two galaxy candidates at redshifts between 15.7 < z < 16.4 in James Webb Space Telescope (JWST) observations from the GLIMPSE survey. These robust sources were identified using a combination of Lyman break selection and photometric redshift estimates. The ultradeep NIRCam imaging from GLIMPSE, combined with the strong gravitational lensing of the AS1063 galaxy cluster, allows us to probe an intrinsically fainter population (down to M UV = −17.0 mag) than previously achievable. These galaxies have absolute magnitudes ranging from M UV = −17.0 to −17.2 mag, with blue (β ≃ −2.87) ultraviolet (UV) continuum slopes, consistent with young, dust-free stellar populations. The number density of these objects, log10(ϕ/[Mpc−3 mag−1]) = − 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.
Authors: Vasily Kokorev, Hakim Atek, John Chisholm, Ryan Endsley, Iryna Chemerynska, Julian B. Muñoz, Lukas J. Furtak, Richard Pan, Danielle Berg, Seiji Fujimoto, Pascal A. Oesch, Andrea Weibel, Angela Adamo, Jeremy Blaizot, Rychard Bouwens, Miroslava Dessauges-Zavadsky, Gourav Khullar, Damien Korber, Ilias Goovaerts, Michelle Jecmen, Ivo Labbé, Floriane Leclercq, Rui Marques-Chaves, Charlotte Mason, Kristen B. W. McQuinn, Rohan Naidu, Priyamvada Natarajan, Erica Nelson, Joki Rosdahl, Alberto Saldana-Lopez, Daniel Schaerer, Maxime Trebitsch, Marta Volonteri, Adi Zitrin
Institution: University of Copenhagen
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $2,400
Funders: National Science Foundation, National Aeronautics and Space Administration, John Templeton Foundation, Gordon and Betty Moore Foundation, Harvard University, Space Telescope Science Institute, National Research Foundation, Schweizerischer Nationalfonds zur Förderung der Wissenschaftlichen Forschung, Danmarks Grundforskningsfond, United States-Israel Binational Science Foundation, Centre National d’Etudes Spatiales, Israel Science Foundation, Knut och Alice Wallenbergs Stiftelse, Vetenskapsrådet, Centre National de la Recherche Scientifique, Staatssekretariat für Bildung, Forschung und Innovation, Institut National de Physique Nucléaire et de Physique des Particules
Awards: G2402334033, NSF-BSF: Dark-Matter Interactions at Cosmic Dawn, G2946456721, G3816317015, Cosmic Dawn Center (DAWN), G4648019588, G7321284446, NSF-BSF: Galaxies in the Reionization Era, Star formation within evolving galaxies: the revolution of the James Webb Space Telescope, G8067020961, G8380842850, G8552695075, Decoding the First Galaxies via 21-cm Fluctuations, G8835071962
OpenAlex ID: W4409240410