MOSDEF-LRIS综述：用静止紫外光谱探测Z~2处成星半导体的ISM/CGM结构
The MOSDEF-LRIS Survey: Probing ISM/CGM Structure of Star-Forming Galaxies at z~2 Using Rest-UV Spectroscopy
摘要：
恒星形成星系中星际和环星系介质（分别为ISM和CGM）中气体、金属和尘埃的复杂结构可以通过Ly $α$发射和吸收、低电离星际（LIS）金属吸收和尘埃红化E（B-V）探测。本文统计分析了$z\sim2.3$上157个恒星形成星系的Ly $α$等效宽度（EW $_{Lyα}$）、LIS等效宽度（EW $_{LIS}$）和E（B-V）之间的相互关系。从个人，深休息紫外光谱和光谱能量分布（SED）建模获得的测量，我们发现，最紧密的相关性之间存在EW $_{LIS}$和E（B-V），虽然所有三个参数之间的相关性是统计上显着的。这些结果表明尘埃和富含金属的HI气体之间存在直接联系，并且它们可能是共空间的。通过比较我们的结果与不同的ISM/CGM模型的预测，我们倾向于一个尘埃ISM/CGM模型，尘埃驻留在HI气体团簇和Ly $α$光子逃逸通过低HI覆盖分数/柱密度的团簇内介质。最后，我们调查的因素，可能有助于内在的散射在这项工作中研究的相关性，包括金属丰度，外流运动学，赖氨酸$α$生产效率，和狭缝损失。具体而言，我们发现证据表明，EW $_{Lyα}$和E（B-V）之间的关系分散反映了金属-HI覆盖分数比的变化作为金属丰度的函数，以及流出物对ISM/CGM孔隙度的影响。未来的模拟纳入恒星形成反馈和辐射转移的Ly $α$光子将提供关键的约束空间分布的中性氢气和尘埃的ISM/CGM结构。
英文摘要：
The complex structure of gas, metals, and dust in the interstellar and circumgalactic medium (ISM and CGM, respectively) in star-forming galaxies can be probed by Ly$α$ emission and absorption, low-ionization interstellar (LIS) metal absorption, and dust reddening E(B-V). We present a statistical analysis of the mutual correlations among Ly$α$ equivalent width (EW$_{Lyα}$), LIS equivalent width (EW$_{LIS}$), and E(B-V) in a sample of 157 star-forming galaxies at $z\sim2.3$. With measurements obtained from individual, deep rest-UV spectra and spectral-energy distribution (SED) modeling, we find that the tightest correlation exists between EW$_{LIS}$ and E(B-V), although correlations among all three parameters are statistically significant. These results signal a direct connection between dust and metal-enriched HI gas, and that they are likely co-spatial. By comparing our results with the predictions of different ISM/CGM models, we favor a dusty ISM/CGM model where dust resides in HI gas clumps and Ly$α$ photons escape through the low HI covering fraction/column density intra-clump medium. Finally, we investigate the factors that potentially contribute to the intrinsic scatter in the correlations studied in this work, including metallicity, outflow kinematics, Ly$α$ production efficiency, and slit loss. Specifically, we find evidence that scatter in the relationship between EW$_{Lyα}$ and E(B-V) reflects the variation in metal-to-HI covering fraction ratio as a function of metallicity, and the effects of outflows on the porosity of the ISM/CGM. Future simulations incorporating star-formation feedback and the radiative transfer of Ly$α$ photons will provide key constraints on the spatial distributions of neutral hydrogen gas and dust in the ISM/CGM structure.
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