Early Results from GLASS-JWST. XXI. Rapid Asembly of a Galaxy at z = 6.23 Revealed by Its C/O Abundance

Tucker Jones, Ryan Sanders, Yuguang Chen, Xin Wang, Takahiro Morishita, Guido Roberts-Borsani, Tommaso Treu, Alan Dressler, Emiliano Merlin, Diego Paris, Paola Santini, Pietro Bergamini, A. Henry, Erin Huntzinger, Themiya Nanayakkara, Kristan Boyett, Marusa Bradac, Gabriel Brammer, Antonello Calabró, Karl GlazebrookKathryn Grasha, Sara Mascia, Laura Pentericci, Michele Trenti, Benedetta Vulcani

Research output: Contribution to journalArticlepeer-review

1 Scopus citations


The abundance of carbon relative to oxygen (C/O) is a promising probe of star formation history in the early universe, as the ratio changes with time due to production of these elements by different nucleosynthesis pathways. We present a measurement of log ( C / O ) = − 1.01 ± 0.12 (stat) ±0.15 (sys) in a z = 6.23 galaxy observed as part of the GLASS-JWST Early Release Science Program. Notably, we achieve good precision thanks to the detection of the rest-frame ultraviolet O iii], C iii], and C iv emission lines delivered by JWST/NIRSpec. The C/O abundance is ∼0.8 dex lower than the solar value and is consistent with the expected yield from core-collapse supernovae, indicating that longer-lived intermediate-mass stars have not fully contributed to carbon enrichment. This in turn implies rapid buildup of a young stellar population with age ≲100 Myr in a galaxy seen ∼900 Myr after the big bang. Our chemical abundance analysis is consistent with spectral energy distribution modeling of JWST/NIRCam photometric data, which indicates a current stellar mass log M * / M ☉ = 8.4 − 0.2 + 0.4 and specific star formation rate ≃20 Gyr−1. These results showcase the value of chemical abundances and C/O in particular to study the earliest stages of galaxy assembly.

Original languageEnglish
Article numberL17
JournalAstrophysical Journal Letters
Issue number1
StatePublished - Jul 1 2023

Bibliographical note

Funding Information:
We thank Michael Topping for allowing a comparison of the line fluxes derived in this work to those measured from an independent data reduction. We are grateful to the referee for providing a constructive review which improved this manuscript. This work is based on observations made with the NASA/ESA/CSA James Webb Space Telescope. This work also uses observations made with the NASA/ESA Hubble Space Telescope. The data were obtained from the Mikulski Archive for Space Telescopes at the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-03127 for JWST. The NIRSpec and NIRCam observations are associated with programs JWST-ERS-1324 and JWST-GO-2561, respectively. We acknowledge financial support for program GLASS-JWST ERS-1324 provided by NASA through grant JWST-ERS-1324 from the Space Telescope Science Institute. Support for this work was provided by NASA through the NASA Hubble Fellowship grant HST-HF2-51469.001-A awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Incorporated, under NASA contract NAS5-26555. We acknowledge support from the INAF Large Grant 2022 “Extragalactic Surveys with JWST” (PI Pentericci). X.W. is supported by CAS Project for Young Scientists in Basic Research, grant No. YSBR-062. M.B. acknowledges support from the Slovenian national research agency ARRS through grant N1-0238. K.G. and T.N. acknowledge support from Australian Research Council Laureate Fellowship FL180100060. The Cosmic Dawn Center is funded by the Danish National Research Foundation (DNRF) under grant #140. Cloud-based data processing and file storage for this work is provided by the AWS Cloud Credits for Research program.

Publisher Copyright:
© 2023. The Author(s). Published by the American Astronomical Society.

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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