A Long Time Ago in a Galaxy Far, Far Away: A Candidate z ∼ 12 Galaxy in Early JWST CEERS Imaging
Authors: Finkelstein Steven L. , Bagley Micaela B. , Arrabal Haro Pablo , Dickinson Mark , Ferguson Henry C. , Kartaltepe Jeyhan S. , Papovich Casey , Burgarella Denis , Kocevski Dale D. , Huertas-Company Marc , Iyer Kartheik G. , Koekemoer Anton M. , Larson Rebecca L. , Pérez-González Pablo G. , Rose Caitlin , Tacchella Sandro , Wilkins Stephen M. , Chworowsky Katherine , Medrano Aubrey , Morales Alexa M. , Somerville Rachel S. , Yung L. Y. Aaron , Fontana Adriano , Giavalisco Mauro , Grazian Andrea , Grogin Norman A. , Kewley Lisa J. , Kirkpatrick Allison , Kurczynski Peter , Lotz Jennifer M. , Pentericci Laura , Pirzkal Nor , Ravindranath Swara , Ryan Russell E. , Trump Jonathan R. , Yang Guang ,   and The CEERS Team:, Almaini Omar , Amorín Ricardo O. , Annunziatella Marianna , Backhaus Bren E. , Barro Guillermo , Behroozi Peter , Bell Eric F. , Bhatawdekar Rachana , Bisigello Laura , Bromm Volker , Buat Véronique , Buitrago Fernando , Calabrò Antonello , Casey Caitlin M. , Castellano Marco , Chávez Ortiz Óscar A. , Ciesla Laure , Cleri Nikko J. , Cohen Seth H. , Cole Justin W. , Cooke Kevin C. , Cooper M. C. , Cooray Asantha R. , Costantin Luca , Cox Isabella G. , Croton Darren , Daddi Emanuele , Davé Romeel , de la Vega Alexander , Dekel Avishai , Elbaz David , Estrada-Carpenter Vicente , Faber Sandra M. , Fernández Vital , Finkelstein Keely D. , Freundlich Jonathan , Fujimoto Seiji , García-Argumánez Ángela , Gardner Jonathan P. , Gawiser Eric , Gómez-Guijarro Carlos , Guo Yuchen , Hamblin Kurt , Hamilton Timothy S. , Hathi Nimish P. , Holwerda Benne W. , Hirschmann Michaela , Hutchison Taylor A. , Jaskot Anne E. , Jha Saurabh W. , Jogee Shardha , Juneau Stéphanie , Jung Intae , Kassin Susan A. , Le Bail Aurélien , Leung Gene C. K. , Lucas Ray A. , Magnelli Benjamin , Mantha Kameswara Bharadwaj , Matharu Jasleen , McGrath Elizabeth J. , McIntosh Daniel H. , Merlin Emiliano , Mobasher Bahram , Newman Jeffrey A. , Nicholls David C. , Pandya Viraj , Rafelski Marc , Ronayne Kaila , Santini Paola , Seillé Lise-Marie , Shah Ekta A. , Shen Lu , Simons Raymond C. , Snyder Gregory F. , Stanway Elizabeth R. , Straughn Amber N. , Teplitz Harry I. , Vanderhoof Brittany N. , Vega-Ferrero Jesús , Wang Weichen , Weiner Benjamin J. , Willmer Christopher N. A. , Wuyts Stijn , Zavala Jorge A. 
Published: December 2022

We report the discovery of a candidate galaxy with a photo-z of z ∼ 12 in the first epoch of the James Webb Space Telescope (JWST) Cosmic Evolution Early Release Science Survey. Following conservative selection criteria, we identify a source with a robust z
phot =

11.8

−
0.2

+
0.3

(1σ uncertainty) with m
F200W = 27.3 and ≳7σ detections in five filters. The source is not detected at λ < 1.4 μm in deep imaging from both Hubble Space Telescope (HST) and JWST and has faint ∼3σ detections in JWST F150W and HST F160W, which signal a Lyα break near the red edge of both filters, implying z ∼ 12. This object (Maisie’s Galaxy) exhibits F115W − F200W > 1.9 mag (2σ lower limit) with a blue continuum slope, resulting in 99.6% of the photo-z probability distribution function favoring z > 11. All data-quality images show no artifacts at the candidate’s position, and independent analyses consistently find a strong preference for z > 11. Its colors are inconsistent with Galactic stars, and it is resolved (r

h
= 340 ± 14 pc). Maisie’s Galaxy has log M
*/M
⊙ ∼ 8.5 and is highly star-forming (log sSFR ∼ −8.2 yr−1), with a blue rest-UV color (β ∼ −2.5) indicating little dust, though not extremely low metallicity. While the presence of this source is in tension with most predictions, it agrees with empirical extrapolations assuming UV luminosity functions that smoothly decline with increasing redshift. Should follow-up spectroscopy validate this redshift, our universe was already aglow with galaxies less than 400 Myr after the Big Bang.