UNCOVER: Illuminating the Early Universe—JWST/NIRSpec Confirmation of z > 12 Galaxies

Bingjie Wang, Seiji Fujimoto, Ivo Labbé, Lukas J. Furtak, Tim B. Miller, David J. Setton, Adi Zitrin, Hakim Atek, Rachel Bezanson, Gabriel Brammer, Joel Leja, Pascal A. Oesch, Sedona H. Price, Iryna Chemerynska, Sam E. Cutler, Pratika Dayal, Pieter van Dokkum, Andy D. Goulding, Jenny E. Greene, Y. FudamotoGourav Khullar, Vasily Kokorev, Danilo Marchesini, Richard Pan, John R. Weaver, Katherine E. Whitaker, Christina C. Williams

Research output: Contribution to journalArticlepeer-review

5 Scopus citations


Observations of high-redshift galaxies provide a critical direct test to the theories of early galaxy formation, yet to date, only three have been spectroscopically confirmed at z > 12. Due to strong gravitational lensing over a wide area, the galaxy cluster field A2744 is ideal for searching for the earliest galaxies. Here we present JWST/NIRSpec observations of two galaxies: a robust detection at z spec = 12.393 − 0.001 + 0.004 , and a plausible candidate at z spec = 13.079 − 0.001 + 0.013 . The galaxies are discovered in JWST/NIRCam imaging and their distances are inferred with JWST/NIRSpec spectroscopy, all from the JWST Cycle 1 UNCOVER Treasury survey. Detailed stellar population modeling using JWST NIRCam and NIRSpec data corroborates the primeval characteristics of these galaxies: low mass (∼108 M ), young, rapidly assembling, metal-poor, and star-forming. Interestingly, both galaxies are spatially resolved, having lensing-corrected rest-UV effective radii on the order of 300-400 pc, which are notably larger than other spectroscopically confirmed systems at similar redshifts. The observed dynamic range of z ≳ 10 sizes spans over 1 order of magnitude, implying a significant scatter in the size-mass relation at early times. Deep into the epoch of reionization, these discoveries elucidate the emergence of the first galaxies.

Original languageEnglish (US)
Article numberL34
JournalAstrophysical Journal Letters
Issue number2
StatePublished - Nov 1 2023

All Science Journal Classification (ASJC) codes

  • Astronomy and Astrophysics
  • Space and Planetary Science


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