[论文解读] From Bubbles and Filaments to Cores and Disks: Gas Gathering and Growth of Structure Leading to the Formation of Stellar Systems

J. E. Pineda, D. Arzoumanian+9 more|arXiv (Cornell University)|May 8, 2022

Astrophysics and Star Formation Studies参考文献 11被引用 37

一句话总结

本文综合多尺度观测与模拟，呈现从巨大气泡到原恒星盘的各向异性生长的连贯图景，将气体聚集和层级吸积与恒星及盘形成联系起来。

ABSTRACT

The study of the development of structures on multiple scales in the cold interstellar medium has experienced rapid expansion in the past decade, on both the observational and the theoretical front. Spectral line studies at (sub-)millimeter wavelengths over a wide range of physical scales have provided unique probes of the kinematics of dense gas in star-forming regions, and have been complemented by extensive, high dynamic range dust continuum surveys of the column density structure of molecular cloud complexes, while dust polarization maps have highlighted the role of magnetic fields. This has been accompanied by increasingly sophisticated numerical simulations including new physics (e.g., supernova driving, cosmic rays, non-ideal magneto-hydrodynamics, radiation pressure) and new techniques such as zoom-in simulations allowing multi-scale studies. Taken together, these new data have emphasized the anisotropic growth of dense structures on all scales, from giant ISM bubbles driven by stellar feedback on $\sim$50-100 pc scales through parsec-scale molecular filaments down to $<$0.1 pc dense cores and $<$1000 au protostellar disks. Combining observations and theory, we present a coherent picture for the formation and evolution of these structures and synthesize a comprehensive physical scenario for the initial conditions and early stages of star and disk formation.

研究动机与目标

• 通过在冷相星际介质中追踪结构在各尺度上的生长，激发对星形成低效性及初等质量函数（IMF）起源的理解。
• 将观测结果（谱线、尘埃连续辐射、偏振）与先进的 HD/MHD 模拟相结合，以连接气泡、丝状结构、核心和盘。
• 阐明膨胀的气泡、丝状结构形成与各向异性吸积如何为星和盘形成的初始条件做出贡献。

提出的方法

• 回顾来自 HI 壳层、H II 区、丝状结构、核心与盘等的多尺度观测数据。
• 整合最先进的 HD 与 MHD 模拟，包括反馈、非理想 MHD，以及 zoom-in 技术，以研究多尺度结构生长。
• 讨论由冲击压缩层形成的丝状结构的形成机制及其通过重力驱动吸积的演化。

Figure 1: Color composite image showing the H i emission at 7.4 $\rm km\,s^{-1}$ (red) and at 3.3 $\rm km\,s^{-1}$ (blue) and the column density map derived from combined Herschel + Planck data (green). The white circles trace the two H i shells associated with the Corona Australis (CrA) molecular c

实验结果

研究问题

• RQ1 膨胀的星际气泡如何影响丝状分子云的形成与形态？
• RQ2 在冲击压缩层中，丝状结构形成的主导机制是什么，它们如何向致密核心乃至原恒星盘供给？
• RQ3 各向异性气体吸积如何将从大尺度（≥50–100 pc）到小尺度（<0.1 pc）的结构连接起来并推动星–盘形成？

主要发现

• 致密结构在从气泡到丝状结构再到核心再到盘的尺度上呈现各向异性生长。
• 气体吸积以分层流动进行：从气泡到丝状结构的壳状吸积、从丝状结构到核心的轴向收缩，以及通过支流从核心到磁盘的非对称吸积。
• 在冲击压缩层中，丝状结构的形成在较高冲击速度时由 type-O 和 type-C 机制主导，形成的丝状结构线质量分布类似观测到的 Salpeter 风格分布。
• 丝状结构吸积质量并从亚临界态演化到超临界态，重力驱动的吸积在初始形成后维持生长。
• 对速度梯度和磁场取向的观测支持沿丝状结构和枢纽的各向异性气体吸积，与提出的多尺度生长范式一致。

Figure 2: a) Illustration of a generic bipolar H ii region and its environment. The ionized gas, the molecular gas, and the PAH emission of the PDR are shown in red, blue, and grey, respectively. b) Composite image of G $319.88+00.79$ , which is an observed example of a bipolar H ii region. c) Cente