A long time ago in a galaxy far, far away: A candidate z ~ 12 galaxy in early JWST CEERS imaging

Steven L. Finkelstein , Micaela B. Bagley , Pablo Arrabal Haro , Mark Dickinson , Henry C. Ferguson , Jeyhan S. Kartaltepe , Casey Papovich , Denis Burgarella (1) , Dale D. Kocevski , Marc Huertas-Company , Kartheik G. Iyer , Anton M. Koekemoer , Rebecca L. Larson , Pablo G. Pérez-González , Caitlin Rose , Sandro Tacchella , Stephen M. Wilkins , Katherine Chworowsky , Aubrey Medrano , Alexa M. Morales , Rachel S. Somerville , L. Y. Aaron Yung , Adriano Fontana , Mauro Giavalisco , Andrea Grazian , Norman A. Grogin , Lisa J. Kewley , Allison Kirkpatrick , Peter Kurczynski , Jennifer M. Lotz , Laura Pentericci , Nor Pirzkal , Swara Ravindranath , Russell E. Ryan , Jonathan R. Trump , Guang Yang , Omar Almaini , Ricardo O. Amorín , Marianna Annunziatella , Bren E. Backhaus , Guillermo Barro , Peter Behroozi , Eric F. Bell , Rachana Bhatawdekar , Laura Bisigello , Volker Bromm , Véronique Buat (1) , Fernando Buitrago , Antonello Calabrò , Caitlin M. Casey , Marco Castellano , Óscar A. Chávez Ortiz , Laure Ciesla (1) , Nikko J. Cleri , Seth H. Cohen , Justin W. Cole , Kevin C. Cooke , M. C. Cooper , Asantha R. Cooray , Luca Costantin , Isabella G. Cox , Darren Croton , Emanuele Daddi (2) , Romeel Davé , Alexander de La Vega , Avishai Dekel , David Elbaz (2) , Vicente Estrada-Carpenter , Sandra M. Faber , Vital Fernández , Keely D. Finkelstein , Jonathan Freundlich (3) , Seiji Fujimoto , Ángela García-Argumánez , Jonathan P. Gardner , Eric Gawiser , Carlos Gómez-Guijarro (2) , Yuchen Guo , Kurt Hamblin , Timothy S. Hamilton , Nimish P. Hathi , Benne W. Holwerda , Michaela Hirschmann , Taylor A. Hutchison , Anne E. Jaskot , Saurabh W. Jha , Shardha Jogee , Stéphanie Juneau , Intae Jung , Susan A. Kassin , Aurélien Le Bail (2) , Gene C. K. Leung , Ray A. Lucas , Benjamin Magnelli (2) , Kameswara Bharadwaj Mantha , Jasleen Matharu , Elizabeth J. Mcgrath , Daniel H. Mcintosh , Emiliano Merlin , Bahram Mobasher , Jeffrey A. Newman , David C. Nicholls , Viraj Pandya , Marc Rafelski , Kaila Ronayne , Paola Santini , Lise-Marie Seillé (1) , Ekta A. Shah , Lu Shen , Raymond C. Simons , Gregory F. Snyder , Elizabeth R. Stanway , Amber N. Straughn , Harry I. Teplitz , Brittany N. Vanderhoof , Jesús Vega-Ferrero , Weichen Wang , Benjamin J. Weiner , Christopher N. A. Willmer , Stijn Wuyts , Jorge A. Zavala

1 LAM - Laboratoire d'Astrophysique de Marseille
2 AIM (UMR_7158 / UMR_E_9005 / UM_112) - Astrophysique Interprétation Modélisation
3 ObAS - Observatoire astronomique de Strasbourg

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.

Keywords: Early universe; Galaxy formation; Galaxy evolution; Astrophysics - Astrophysics of Galaxies

Domains: Sciences of the Universe [physics]; Astrophysics [astro-ph]

Steven L. Finkelstein, Micaela B. Bagley, Pablo Arrabal Haro, Mark Dickinson, Henry C. Ferguson, et al.. A long time ago in a galaxy far, far away: A candidate z ~ 12 galaxy in early JWST CEERS imaging. The Astrophysical journal letters, 2022, 940, pp.L55. ⟨10.3847/2041-8213/ac966e⟩. ⟨insu-03894338⟩