红移8≤z≤10星系中莱曼α阻尼翼的起源：利用NINJA模拟的探索
On the Origin of the Ly$α$ Damping Wing in Galaxies at $8\le z \le 10$: Explorations using the NINJA Simulations
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中文总结 AI 辅助
该研究结合NINJA模拟与电离泡模型，探索红移8-10星系的Lyα阻尼翼起源，发现最强阻尼Lyα吸收体可探测ISM、CGM与IGM的电离状态，且部分电离气体能提升强吸收体发生率但仍低于观测
中文摘要 AI 辅助
詹姆斯·韦布空间望远镜（JWST）对红移7≤z≤14星系的莱曼α（Lyα）阻尼翼测量，为再电离时代提供了强大的探测手段。我们将大尺度宇宙学流体动力学NINJA模拟，与红移8和10处的理想化电离泡模型相结合，量化了星系际介质（IGM）、星系晕周介质（CGM）和星系际介质（ISM）对观测到的Lyα阻尼翼的贡献。我们生成了模拟的Lyα吸收光谱，并考虑三种理想化情景：（i）嵌入均匀电离IGM中的星系；（ii）被半径0-400 pkpc的HII区包围的星系；（iii）包含位力半径内部分电离气体的Lyα吸收的相同模型。我们探索IGM的中性氢分数（x_HI）为0.1、0.8和1.0，并将推断的氢原子柱密度（N_HI）分布与观测结果进行比较，以约束HII区的大小以及IGM和星系内部及周围气体的x_HI。星系被延伸至约60-100 pkpc的致密气体包围，其范围随晕质量增加而增大，且在红移8和10之间几乎没有演化。推断的N_HI也随晕质量和恒星质量增加而增大。虽然不同的IGM x_HI与HII区大小的组合可再现观测到的阻尼Lyα吸收发生率和N_HI中位数，但具有均匀电离IGM或HII区大于约50 pkpc的模型无法再现最强吸收体（N_HI>10^22 cm^-2）。包含位力半径内的部分电离气体会大幅增加这些吸收体的发生率，尽管预测值仍低于观测结果，这表明恒星诞生云中未分辨气体存在额外贡献。因此，最强的阻尼Lyα吸收体为ISM、CGM和IGM的电离状态提供了独特的探测手段。
英文摘要
Ly$α$ damping wing measurements of galaxies at $7\leq z\leq14$ with the JWST provide a powerful probe of the Epoch of Reionization. We combine the large-scale cosmological hydrodynamical NINJA simulations with an idealized ionized-bubble model at z=8 and 10 to quantify the contributions of the intergalactic medium (IGM), circumgalactic medium (CGM), and interstellar medium (ISM) to the observed Ly$α$ damping wing. We generate mock Ly$α$ absorption spectra, and consider three idealized scenarios: (i) galaxies embedded in a uniformly ionized IGM, (ii) galaxies surrounded by HII regions with radii of 0-400 pkpc, and (iii) the same models including Ly$α$ absorption from partially ionized gas within the virial radius. We explore IGM neutral fractions ($x_{\rm HI}$) of 0.1, 0.8, and 1.0, and compare the distribution of inferred HI column densities (NHI) with observations to constrain the sizes of HII regions and $x_{\rm HI}$ of the IGM and gas in and around galaxies. Galaxies are surrounded by over-dense gas extending to $\sim$60-100 pkpc, with its extent increasing with halo mass and showing little evolution between z=8 and 10. The inferred NHI also increases with halo and stellar mass. While the observed incidence of damped Ly$α$ absorption and the median NHI can be reproduced by different combinations of $x_{\rm HI}$ of the IGM and HII region size, models with a uniformly ionized IGM or HII regions larger than $\sim50$ pkpc fail to reproduce the strongest absorbers (NHI>$10^{22}cm^{-2}$). Including partially ionized gas within the virial radius substantially increases the incidence of these absorbers, although the predicted values remain below the observations, suggesting an additional contribution from unresolved gas in stellar birth clouds. The strongest damped Ly$α$ absorbers therefore provide a unique probe of the ionization state of the ISM, CGM, and IGM.
