Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy

@misc{rai2026precise,
  title = {{Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy}},
  author = {Raunaq Singh Rai and Guido Roberts-Borsani and Ryan Sanders and Alice E. Shapley and Leonardo Clarke and Pascal A. Oesch and Daniel Schaerer and Rui Marques-Chaves and Romain A. Meyer and Emma Giovinazzo and Shreya Karthikeyan},
  howpublished = {arXiv},
  year = {2026},
  month = sep,
  doi = {10.48550/arxiv.2609.35526},
  eprint = {2609.35526},
  archivePrefix = {arXiv},
  url = {https://arxiv.org/abs/2609.35526},
}

TY  - UNPB
TI  - Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy
AU  - Raunaq Singh Rai
AU  - Guido Roberts-Borsani
AU  - Ryan Sanders
AU  - Alice E. Shapley
AU  - Leonardo Clarke
AU  - Pascal A. Oesch
AU  - Daniel Schaerer
AU  - Rui Marques-Chaves
AU  - Romain A. Meyer
AU  - Emma Giovinazzo
AU  - Shreya Karthikeyan
PY  - 2026
DA  - 2026/09/28
PB  - arXiv
DO  - 10.48550/arxiv.2609.35526
UR  - https://arxiv.org/abs/2609.35526
AB  - We present ultra-deep JWST/NIRSpec R∼1000 spectroscopy of nine star-forming galaxies at z=6.0−8.3 in the GOODS-N field, drawn from the Origins of Metal Enrichment in Galaxies at cosmic dAwn (OMEGA) survey. Paired with ancillary ultra-deep G140M observations, the G395M integrations from OMEGA yield continuous rest-frame UV-to-optical coverage and the full suite of diagnostics needed for precise characterisations and measures of the chemical abundances of these systems. Crucially, the auroral [O\,{\scriptsize III}]\,λ4363 line is detected in every galaxy, enabling the determination of electron temperatures and direct oxygen abundances of 12+log(O/H)=7.14−8.18, independent of strong-line calibrations that dominate systematics at these redshifts. We couple direct oxygen abundances with measurements of rest-frame UV emission-line strengths and ratios to infer the physical properties of our sample. Most importantly, we trace the relationship between oxygen abundance and both C/O and N/O abundance ratios with high fidelity, demonstrating robustly that z=6.0−8.3 galaxies follow the local trend in C/O vs. O/H, and that inferences regarding N/O are sensitive to the choice of rest-frame UV (\niv] or \niii]) or optical ([\nii]) tracers. This pilot study demonstrates the power of combining ultra-deep JWST/NIRSpec R∼1000 rest-frame UV and optical spectroscopy, which now requires statistical samples to uncover the nebular properties of the full population of z≥ 6 star-forming galaxies.
ER  -