来自超深、静止系紫外到光学JWST光谱的首个十亿年内单个星系精确C-N-O丰度
Precise C-N-O Abundances of Individual Galaxies in the First Billion Years from Ultra-Deep, Rest-UV-to-Optical JWST Spectroscopy
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中文总结 AI 辅助
本研究利用超深JWST/NIRSpec光谱对z=6-8的9个星系进行直接氧丰度测量，发现其C/O比值遵循局域趋势，并揭示N/O推断对示踪物选择的敏感性。
中文摘要 AI 辅助
我们展示了在GOODS-N天区中，来自宇宙黎明星系金属增丰起源（OMEGA）巡天的9个z=6.0-8.3恒星形成星系的超深JWST/NIRSpec R~1000光谱。结合辅助的超深G140M观测，OMEGA的G395M积分提供了连续的静止系紫外到光学覆盖，以及对这些系统进行精确表征和化学丰度测量所需的全部诊断工具。关键的是，每个星系中都探测到了极光[O III] λ4363线，从而能够独立于主导这些红移处系统误差的强线校准，确定电子温度和直接氧丰度12+log(O/H)=7.14-8.18。我们将直接氧丰度与静止系紫外发射线强度和比值测量相结合，以推断我们样本的物理性质。最重要的是，我们高保真地追踪了氧丰度与C/O和N/O丰度比之间的关系，有力地证明了z=6.0-8.3星系遵循C/O对O/H的局域趋势，并且关于N/O的推断对静止系紫外（NIV]或NIII]）或光学（[NII]）示踪物的选择敏感。这项初步研究展示了结合超深JWST/NIRSpec R~1000静止系紫外和光学光谱的威力，现在需要统计样本来揭示z≥6恒星形成星系整体的星云性质。
英文摘要
We present ultra-deep JWST/NIRSpec $R\sim1000$ 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}]\,$λ$4363 line is detected in every galaxy, enabling the determination of electron temperatures and direct oxygen abundances of $12+\log(\mathrm{O/H})=7.14-8.18$, 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 $R\sim1000$ rest-frame UV and optical spectroscopy, which now requires statistical samples to uncover the nebular properties of the full population of $z\geq 6$ star-forming galaxies.
发表机构
- University College London（伦敦大学学院）
- University of Kentucky（肯塔基大学）
- University of California, Los Angeles（加州大学洛杉矶分校）
- University of Geneva（日内瓦大学）
- Niels Bohr Institute, University of Copenhagen（哥本哈根大学尼尔斯·玻尔研究所）
- CNRS, IRAP（法国国家科学研究中心，天体物理研究研究所）
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