A Long Time Ago in a Galaxy Far, Far Away: A Candidate z ∼ 12 Galaxy in Early JWST CEERS Imaging

By S. Finkelstein, M. Bagley, P. Haro, Mark Dickinson, H. Ferguson, J. Kartaltepe, C. Papovich, D. Burgarella, D. Kocevski, Marc Huertas-Company and 108 more. Astrophysical Journal Letters, 2022

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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.

Subfields: Astronomy and Astrophysics, Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/184bbe70cc51169bfe657a12eef46bfd17125ae2

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Citations in the corpus

The Rise of Faint, Red Active Galactic Nuclei at z > 4: A Sample of Little Red Dots in the JWST Extragalactic Legacy Fields (2025, unknown): “55 The CEERS, PRIMER, and NGDEEP NIRCam data were processed using the JWST Calibration Pipeline 56 ( versions 1.8.5, 1.10.2, and 1.9.2, respectively ) with custom modi ﬁ cations described in M. B. Bagley et al. ( 2023 ) and S. L. Finkelstein et al. ( 2022 ) .”
On the stunning abundance of super-early, luminous galaxies revealed by JWST (2022, background): “For example, Maisie’s galaxy (z ≈ 14,MUV = −20.3,SFR = 4.1 M yr−1,M∗ = 108.5 M has AV = 0.06 Finkelstein et al. 2022).”
A Comprehensive Study of Galaxies at z ∼ 9–16 Found in the Early JWST Data: Ultraviolet Luminosity Functions and Cosmic Star Formation History at the Pre-reionization Epoch (2022, methodology): “Our estimates of the SFRs and stellar masses agree with previous estimates by Naidu et al. (2022b), Donnan et al. (2023), and Finkelstein et al. (2022b), indicating that these luminous galaxies are very massive with stellar masses as high as M*∼ (1–10)× 10 8Me at z∼ 10–16.”
CEERS Epoch 1 NIRCam Imaging: Reduction Methods and Simulations Enabling Early JWST Science Results (2022, methodology): “Finkelstein et al. (2022b) presented an earlier arXiv version that used version 0.05 (see previous section), where the improved astrometric alignment had a significant effect on their results.”
The James Webb Space Telescope Mission (2023, background): “Early results from the CEERS data include the discovery of candidate galaxies at z> 8 (e.g., Finkelstein et al. 2022; Naidu et al. 2022; Topping et al. 2022; Ono et al. 2022) and studies of galaxies at 3< z< 7, including quiescent galaxies (Carnall et al. 2023), AGN host galaxies (Ding et al. 2022;…”
CEERS Key Paper. I. An Early Look into the First 500 Myr of Galaxy Formation with JWST (2022, methodology): “For these five unresolved sources, we then follow the methodology of Finkelstein et al. (2022a, 2022b) to explore whether the colors of any of the few unresolved galaxy candidates could be consistent with stars.”
The Complete CEERS Early Universe Galaxy Sample: A Surprisingly Slow Evolution of the Space Density of Bright Galaxies at z ∼ 8.5–14.5 (2023, methodology): “…have noted that the default Kron parameters we use for this aperture correction can miss light in the wings of the PSF ( e.g., Bouwens et al. 2015; Finkelstein et al. 2022a ) , we estimate residual aperture corrections using source injection simulations, adding 3000 mock sources to our real…”