[论文解读] Initial Conditions for Star Formation: A Physical Description of the Filamentary ISM

A. Hacar, S. E. Clark+5 more|arXiv (Cornell University)|Mar 17, 2022

Astrophysics and Star Formation Studies被引用 34

一句话总结

本文综述了星际介质（ISM）中跨尺度的丝状结构，整合了一个大型丝状体统计清单，并分析吸积与演化如何设定恒星形成的初始条件。

ABSTRACT

The interstellar medium contains filamentary structure over a wide range of scales. Understanding the role of this structure, both as a conduit of gas across the scales and a diagnostic tool of local physics, is a major focus of star formation studies. We review recent progress in studying filamentary structure in the ISM, interpreting its properties in terms of physical processes, and exploring formation and evolution scenarios. We include structures from galactic-scale filaments to tenth-of-a-parsec scale filaments, comprising both molecular and atomic structures, from both observational and theoretical perspectives. In addition to the literature overview, we assemble a large amount of catalogue data from different surveys and provide the most comprehensive census of filamentary structures to date. Our census consists of 22 803 filamentary structures, facilitating a holistic perspective and new insights. We use our census to conduct a meta-analysis, leading to a description of filament properties over four orders of magnitudes in length and eight in mass. Our analysis emphasises the hierarchical and dynamical nature of filamentary structures. Filaments do not live in isolation, nor they generally resemble static structures close to equilibrium. We propose that accretion during filament formation and evolution sets some of the key scaling properties of filaments. This highlights the role of accretion during filament formation and evolution and also in setting the initial conditions for star formation. Overall, the study of filamentary structures during the past decade has been observationally driven. While great progress has been made on measuring the basic properties of filaments, our understanding of their formation and evolution is clearly lacking. In this context, we identify a number of directions and questions we consider most pressing for the field.

研究动机与目标

• 总结丝状结构作为局部 ISM 物理过程的传导通道与诊断工具的作用。
• 综合跨尺度的丝状结构形成与演化的观测与理论进展。
• 提供对丝状结构属性的全面普查，以支持元分析和尺度关系的建立。
• 强调在丝状结构演化过程中的吸积如何影响恒星形成的初始条件。

提出的方法

• 评述从亚秒差距到千秒差距尺度的丝状结构的广泛观测与理论研究。
• 汇集并分析来自多样化调查的大型丝状结构目录（22,803 条丝状结构）。
• 进行元分析，以描述丝状结构在长度跨越四个数量级、质量跨越八个数量级时的属性。
• 讨论柱密度剖面的参数化（高斯型与 Plummer 型）并推导相关量。
• 结合静水与等温圆柱理论，讨论临界线质量与稳定性考量。
• 考察磁场与非热运动在丝状结构稳定性与分裂中的作用。

实验结果

研究问题

• RQ1 丝状结构在长度跨越四个数量级、质量跨越八个数量级时的特征属性与尺度关系是什么？
• RQ2 吸积与动力学演化如何塑造丝状结构内的恒星形成初始条件？
• RQ3 磁场和非热运动在不同环境中对丝状结构的稳定性与分裂的影响程度如何？
• RQ4 跨尺度的观测调查如何达成一个统一的丝状形态与动力学描述？

主要发现

• 丝状结构呈现层次化且动态的特性，而非静态或孤立的结构。
• 大型普查（22,803 条丝状结构）使得跨越广阔尺度的元分析成为可能，揭示了一致的尺度趋势。
• 在形成与演化过程中的吸积似乎决定了丝状结构的一些关键尺度属性，影响初始恒星形成条件。
• 丝状结构的性质，如线质量、长度和径向剖面，范围广泛，邻近云中的典型内宽度约为 0.1 pc，尽管这存在争议。
• 在某些情况下，丝状结构往往处于亚音速到跨声速区间，磁场提供的支撑取决于磁场取向，影响对重力的稳定性。
• 强调观测进展，同时在跨环境的形成机制与演化方面仍存在持续的知识缺口。