标题： CLASSY XI：利用紫外吸收线和21厘米观测追踪中性气体性质 显示英文标题

标题： CLASSY XI: Tracing Neutral Gas Properties using UV Absorption Lines and 21-cm Observations

摘要： JWST的静止框架远紫外线(FUV)观测正在彻底改变我们对驱动再电离的高红移星系及其实现机制的理解。 为了全面解读这些观测结果，我们必须能够诊断星际介质(ISM；例如，列密度、覆盖分数、外流速度)的属性如何直接与产生的吸收特征相关联。 利用CLASSY中45个附近恒星形成星系的高信噪比和高分辨率FUV光谱，我们对跨越一系列星系属性的中性及低电离态(LIS)星际紫外吸收线(OI、SiII、SII、CII、AlII)进行了最大规模的一致且同时的表征。 我们还展示了35个星系的21厘米HI观测结果，其中多个星系气体贫乏或未被探测到，这可能表明后恒星爆发阶段的开始。 我们发现，我们的同时单分量Voigt曲线拟合能够准确模拟约75%星系的LIS吸收，缓解了饱和、填充和退化带来的挑战。 虽然最巨大的星系需要额外的成分，但我们的单分量拟合返回了吸收气体的平均属性，并遵循由单一气体云描述的比例关系。 我们探讨了LIS吸收与中性ISM(如OI、Ly-α、HI 21-cm)的直接示踪剂之间的联系，发现CII最能追踪中性气体的趋势，而其他离子表现出较弱的相关性。 鉴于在更高红移直接观测HI面临的挑战，我们证明LIS吸收可以成为研究中性ISM的强大手段，并提出了预测中性气体属性的经验关系。 显示英文摘要

摘要： Rest-frame far-ultraviolet (FUV) observations from JWST are revolutionizing our understanding of the high-z galaxies that drove reionization and the mechanisms by which they accomplished it. To fully interpret these observations, we must be able to diagnose how properties of the interstellar medium (ISM; e.g., column density, covering fraction, outflow velocity) directly relate to the absorption features produced. Using the high-S/N and high-resolution FUV spectra of 45 nearby star-forming galaxies from CLASSY, we present the largest uniform, simultaneous characterization of neutral and low-ionization state (LIS) interstellar UV absorption lines (OI, SiII, SII, CII, AlII) across a wide range of galaxy properties. We also present 21-cm HI observations for 35 galaxies, multiple of which are gas-poor or non-detected, possibly indicating the onset of a post-starburst phase. We find that our simultaneous 1-component Voigt profile fits are capable of accurately modeling the LIS absorption for ~75% of galaxies, mitigating challenges associated with saturation, infilling, and degeneracies. While the most massive galaxies require additional components, our 1-component fits return average properties of the absorbing gas and follow the scaling relations described by a single gas cloud. We explore connections between LIS absorption and direct tracers of the neutral ISM (OI, Ly-alpha, HI 21-cm), finding that CII most closely traces the neutral gas trends while other ions exhibit weaker correlations. Given the challenges with directly observing HI at higher-z, we demonstrate that LIS absorption can be a powerful means to study the neutral ISM and present empirical relationships for predicting neutral gas properties.