The Astrophysical Journal Letters (Jan 2023)

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 Glazebrook,
  • Kathryn Grasha,
  • Sara Mascia,
  • Laura Pentericci,
  • Michele Trenti,
  • Benedetta Vulcani

DOI
https://doi.org/10.3847/2041-8213/acd938
Journal volume & issue
Vol. 951, no. 1
p. L17

Abstract

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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 $\mathrm{log}({\rm{C}}/{\rm{O}})=-1.01\pm 0.12$ (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 $\mathrm{log}\,{M}_{* }/{M}_{\odot }={8.4}_{-0.2}^{+0.4}$ 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.

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