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

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  • 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
  • Antonello Calabró
  • Karl Glazebrook
  • Kathryn Grasha
  • Sara Mascia
  • Laura Pentericci
  • Michele Trenti
  • Benedetta Vulcani

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
Number of pages11
Publication statusPublished - 3 Jul 2023

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

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