![Rest-frame equivalent widths of C iii] ππ1907, 1909 (left) and C iv ππ1548, 1550 (right) against the direct πe-based ([O III]π4363) metallicity. Curves are the star-forming photoionisation grids of Nakajima et al. (2018) at a burst age of 1 Myr and log(πH/cmβ3 ) = 3. Solid curves represent the POPSTAR single-star models (MollΓ‘ et al. 2009), and dashed curves indicate the BPASS binary models (Eldridge et al. 2017), coloured by ionisation parameter as shown in the colour-bar. -- [astro-ph.GA]](https://i0.wp.com/astrobiology.com/wp-content/uploads/2026/10/Precise.png?fit=1200%2C675&ssl=1)
[astro-ph.GA] We present ultra-deep JWST/NIRSpec π βΌ 1000 spectroscopy of nine star-forming galaxies at π§ = 6.0 β 8.3 in the GOODSN 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 III]π4363 line is detected in every galaxy, enabling the determination of electron temperatures and direct oxygen abundances of 12 + log(O/H) = 7.14 β 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 π§ = 6.0 β 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 (N IV] or N III]) or optical ([N II]) tracers.
This pilot study demonstrates the power of combining ultra-deep JWST/NIRSpec π βΌ 1000 rest-frame UV and optical spectroscopy, which now requires statistical samples to uncover the nebular properties of the full population of π§ β₯ 6 star-forming galaxies.
Raunaq Singh Rai, Guido Roberts-Borsani, Ryan Sanders, Alice E. Shapley, Leonardo Clarke, Pascal A. Oesch, Daniel Schaerer, Rui Marques-Chaves, Romain A. Meyer, Emma Giovinazzo, Shreya Karthikeyan
Comments: 16 pages, 9 figures, submitted to MNRAS, comments welcome
Subjects: Astrophysics of Galaxies (astro-ph.GA)
Cite as: arXiv:2609.35526 [astro-ph.GA] (or arXiv:2609.35526v1 [astro-ph.GA] for this version)
https://doi.org/10.48550/arXiv.2609.35526
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Submission history
From: Raunaq Singh Rai
[v1] Mon, 28 Sep 2026 16:12:49 UTC (5,435 KB)
https://arxiv.org/abs/2609.35526
Astrobiology, Astrochemistry, Astronomy,
