Models of chemical enrichment and inhomogeneity in high-redshift galaxies are challenging to constrain observationally. In this work, we discuss a novel approach to probe chemical inhomogeneities within long gamma-ray burst (GRB) host galaxies, by comparing the absorption metallicity, Zabs, from the GRB afterglow (which probes the environment along the line of sight) with the emission-line metallicity, Zemiss, measured via slit spectroscopy. Using the IllustrisTNG simulation, the theoretical relationship between these metallicity metrics is explored for a range of GRB formation models, varying the GRB progenitor metallicity threshold. For galaxies with fixed Zemiss, the median value of Zabs depends strongly on the GRB progenitor threshold metallicity, with Zabs significantly lower than Zemiss for high-metallicity hosts. Conversely, at fixed Zabs, the median value of Zemiss depends primarily on the metallicity distribution of galaxies in IllustrisTNG and their chemical inhomogeneities, offering a GRB model-independent way to constrain these processes observationally. Currently, only one host galaxy has data for both absorption and emission metallicities (GRB121014A). We re-analyse the emission spectrum and compare the inferred metallicity Zemiss to a recent Bayesian determination of Zabs, finding $\log (Z_{\rm emiss}/Z_{\odot }) = \log (Z_{\rm abs}/Z_{\odot }) +0.35^{+ 0.14}_{- 0.25}$, within ∼2 standard deviations of predictions from the IllustrisTNG simulation. Future observations with the James Webb Space Telescope will be able to measure Zemiss for four other GRB hosts with known Zabs values, using ∼2-h observations. While small, the sample will provide preliminary constraints on the Zabs–Zemiss relation to test chemical enrichment schemes in cosmological simulations.

中文翻译：

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一种研究 GRB 宿主星系中化学不均匀性的新方法：Zabs-Zemiss 关系

高红移星系中的化学富集和不均匀性模型很难在观测上加以约束。在这项工作中，我们讨论了一种探测长伽马射线爆发 (GRB) 宿主星系内化学不均匀性的新方法，通过比较 GRB 余辉（沿视线探测环境）的吸收金属丰度 Zabs 与发射线金属丰度，Zemiss，通过狭缝光谱测量。使用 IllustrisTNG 模拟，探索了这些金属丰度指标之间的理论关系，用于一系列 GRB 形成模型，改变 GRB 前体金属丰度阈值。对于具有固定 Zemiss 的星系，Zabs 的中值强烈依赖于 GRB 祖先阈值金属丰度，对于高金属度宿主，Zabs 显着低于 Zemiss。相反，在固定的 Zabs 处，Zemiss 的中值主要取决于 IllustrisTNG 中星系的金属丰度分布及其化学不均匀性，提供了一种独立于 GRB 模型的方法来观察约束这些过程。目前，只有一个宿主星系拥有吸收和发射金属量的数据（GRB121014A）。我们重新分析发射光谱并将推断的金属丰度 Zemiss 与最近的贝叶斯确定的 Zabs 进行比较，发现 $\log (Z_{\rm emiss}/Z_{\odot }) = \log (Z_{\rm abs}/ Z_{\odot }) +0.35^{+ 0.14}_{- 0.25}$，在 IllustrisTNG 模拟预测的 ∼2 个标准差内。未来詹姆斯韦伯太空望远镜的观测将能够使用~2小时的观测来测量其他四个已知 Zabs 值的 GRB 宿主的 Zemiss。虽然很小，