AI 中文总结
该研究利用JWST引力透镜星系巡天分析低质量星系光谱，通过直接方法测量得出新的金属丰度校准，追踪红移\(z\sim6\)的质量 - 金属丰度关系，还发现了星系中氮丰度等特征及WR恒星对化学丰度的可能贡献。
AI 中文摘要
我们分析了来自DREAMS和其他引力透镜星系巡天的405个红移\(z = 4.5\)至\(10.1\)的恒星形成星系的深度JWST/NIRSpec光谱，以研究本质上微弱的低质量星系中的化学丰度。样本涵盖\(M_{\rm UV}\simeq - 12\)至\(-22\)，达到\(M_\star\simeq10^{5.7}\,M_\odot\)，50%的\(M_{\rm UV} > - 17.5\)的源被放大\(\mu>3\)。通过单个光谱和按质量分类的叠加光谱，利用静止帧紫外和光学谱线得出气相金属丰度以及氮和碳的丰度。我们从按恒星质量分类的叠加光谱的直接方法测量中得出新的经验性强线金属丰度校准，达到代表性恒星质量\(M_\star\simeq10^{6.6}\,M_\odot\)。应用这些校准，我们追踪了红移\(z\sim6\)的质量 - 金属丰度关系，低至\(M_\star\simeq10^{6.6}\,M_\odot\)，此时达到\(12+\log({\rm O/H})\simeq7.2\)，低质量斜率比本地关系稍陡，与流体动力学模拟大致一致。在\(M_\star\simeq10^{7.7}\,M_\odot\)的叠加光谱中，N\,{\sc iv}]\,$\lambda\lambda\,1483,1486$的N/O比[N\,{\sc ii}]\,$\lambda6583$的N/O高出约\(1.4\) dex。紫外 - 光学差异可能表明存在一个局部的、高度电离的富氮成分，其高N/O和低于太阳的C/O类似于恒星质量\(M_\star\lesssim10^6\,M_\odot\)的富氮球状星团群体。这些丰度模式与He\,{\sc ii}\,\W4686/H$\beta$比率约为\(0.03\)（远高于BPASS预测）的组合表明，WR恒星可能既有助于快速的CNO循环富集，也有助于硬电离辐射，推断的WR群体可能提供足够的氮来解释球状星团尺度上的过量氮。
英文摘要
We analyze 405 deep JWST/NIRSpec spectra of star-forming galaxies at $z=4.5$--$10.1$ from DREAMS and other lensing-cluster surveys to study chemical enrichment in intrinsically faint, low-mass galaxies. The sample covers $M_{\rm UV}\simeq-12$ to $-22$ and reaches $M_\star\simeq10^{5.7}\,M_\odot$, with 50\% of the sources at $M_{\rm UV}>-17.5$ magnified by $μ>3$. From individual spectra and mass-binned stacks, we derive the gas-phase metallicity together with nitrogen and carbon abundances using the rest-frame UV and optical lines. \Add{We derive new empirical strong-line metallicity calibrations using direct-method measurements from stellar-mass-binned stacks, reaching a representative stellar mass of $M_\star\simeq10^{6.6}\,M_\odot$. Applying these calibrations, we trace the $z\sim6$ mass--metallicity relation down to $M_\star\simeq10^{6.6}\,M_\odot$, where it reaches $12+\log({\rm O/H})\simeq7.2$, with a low-mass slope slightly steeper than the local relation and in broad agreement with hydrodynamical simulations.} In the $M_\star\simeq10^{7.7}\,M_\odot$ stack, N/O from N\,{\sc iv}]\,$λλ\,1483,1486$ exceeds that from [N\,{\sc ii}]\,$\lambda6583$ by $\simeq1.4$ dex. The UV--optical difference could indicate a localized, highly ionized N-rich component whose high N/O and subsolar C/O resemble nitrogen-rich globular-cluster populations with $M_\star\lesssim10^6\,M_\odot$. \Add{The combination of these abundance patterns and a He\,{\sc ii}\,\W4686/H$β$ ratio of $\simeq0.03$, well above BPASS predictions, suggests that WR stars may contribute both prompt CNO-cycle enrichment and hard ionizing radiation, with the inferred WR population potentially supplying enough nitrogen to account for the excess on globular-cluster scales.
Comments35 pages, submitted to the Astrophysical Journal
