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arXiv 2603.03063astro-ph.GAastro-ph.SR
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射线状丝状物在枢纽-丝状物系统中的起源

An Origin of Radially Aligned Filaments in Hub-Filament Systems

Kyushu University（九州大学）；Nagoya University（名古屋大学）

Shingo Nozaki, Shu-ichiro Inutsuka

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11 pages, 5 figures, Accepted for publication in ApJL
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AI总结：

本文提出通过磁流体动力学冲击与沙漏形磁场相互作用形成枢纽-丝状物系统中径向对齐丝状物的机制，并解释了其形态和质量吸积特性。

摘要：

最近的观测结果表明，枢纽-丝状物系统（HFSs）是大质量恒星和星团的主要形成场所。一些HFSs以多个沿径向指向中心高密度枢纽的丝状物为特征。然而，径向对齐丝状物的物理起源仍然未知。在这里，我们提出了一种新的HFSs形成机制，该机制由快速磁流体动力学冲击与具有沙漏形磁场和密度不均匀性的分子云的相互作用驱动。我们的三维磁流体动力学模拟显示，冲击传播导致形成径向对齐的丝状结构，其线质量略高于热临界线质量，长度为1-3 pc，宽度为0.06-0.08 pc。高密度丝状气体（n_H2 ≈ 10^4 cm⁻³）表现出向内的速度为1-4 km s⁻¹，向枢纽中心增加。而介于丝状物之间的低密度星际气体保持低速，无论半径如何。质量吸积到枢纽是通过密集丝状物进行的。丝状物的形成是由弯曲磁场线产生的斜面冲击驱动的。由此产生的冲击后磁场的增强诱导了磁性引导的流入。冲击界面相互作用放大密度扰动，类似于Richtmyer-Meshkov不稳定性模式，从而促进被冲击层的碎裂成多个丝状物。本信件研究的过程解释了径向对齐丝状物的形态以及HFSs中观察到的有选择性的质量吸积。在我们的模拟中，所得到的恒星形成效率约为4%，表明冲击驱动的演化的限制SFE仅限于几个百分比。

英文摘要：

Recent observations have identified hub-filament systems (HFSs) as the primary formation sites of massive stars and star clusters. Some HFSs are characterized by multiple filaments aligned radially toward a central high-density hub. However, the physical origin of radially aligned filaments remains unknown. Here, we propose a new formation mechanism of HFSs driven by the interaction of a fast magnetohydrodynamic shock with a molecular cloud characterized by an hourglass-shaped magnetic field and density inhomogeneity. Our three-dimensional magnetohydrodynamic simulations show that the shock propagation leads to the formation of radially aligned filamentary structures with line masses slightly above the thermally critical line mass and lengths of $1$-$3\,\rm{pc}$, and widths of $0.06$-$0.08\,\rm{pc}$. High-density filamentary gas ($n_{\rm{H_2}} \sim 10^4 \, \rm{cm^{-3}}$) selectively exhibits inward velocities of $1-4\, \rm{km \, s^{-1}}$ that increase toward the hub center, while the ambient low-density inter-filament gas retains low velocities regardless of the radius. Mass accretion onto the hub is channeled through dense filaments. The filament formation is driven by oblique shocks generated at the bent magnetic field lines. The resulting post-shock amplification of the tangential magnetic field induces a magnetically guided inflow. The shock-interface interaction amplifies density perturbations, resembling Richtmyer--Meshkov instability modes, which promotes the fragmentation of the shocked layer into multiple filaments. The process studied in this Letter explains both the morphology of radially aligned filaments and the selective mass accretion observed in HFSs. In our simulation, the resulting star formation efficiency is $\sim4\%$, suggesting that the shock-driven evolution limits the SFE to only a few percent.

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