Increasing Mass-to-flux Ratio from the Dense Core to the Protostellar Envelope around the Class 0 Protostar HH 211
Increasing Mass-to-flux Ratio from the Dense Core to the Protostellar Envelope around the Class 0 Protostar HH 211
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DOI：
10.3847/1538-4357/aca47f
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发表时间：
2022-11
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通讯作者：
Hsi-Wei Yen;P. Koch;Chin-Fei Lee;N. Hirano;N. Ohashi;Jinshi Sai (Insa Choi);S. Takakuwa;Ya-wen Tang;K. Tatematsu;B. Zhao
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作者：
Hsi-Wei Yen;P. Koch;Chin-Fei Lee;N. Hirano;N. Ohashi;Jinshi Sai (Insa Choi);S. Takakuwa;Ya-wen Tang;K. Tatematsu;B. Zhao
为了研究原恒星源中从大尺度到小尺度的磁通量传输，我们分析了 Nobeyama 45 m N2H+ (1–0)、JCMT 850 μm 极化、阿塔卡马大型毫米/亚毫米阵列 (ALMA) C18O (2–1) 以及 0 级原恒星 HH 211 的 1.3 和 0.8 mm（极化）连续谱数据。使用Davis-Chandrasekhar-Fermi方法，利用单碟线和极化数据估算了0.1 pc尺度的致密核心，并通过ALMA数据分析气体运动学和磁场结构，根据重力和磁场张力之间的力平衡估算了600 au尺度的原恒星包层。我们的分析表明，从0.1 pc-600 au尺度，磁场强度从40-107 μG增加到0.3-1.2 mG，磁场强度和密度之间的比例关系为B ∝ ρ 0.36±0.08，质量通量比从1.2-3.7增加到9.1-32.3。质量通量比的增加可能表明磁场与 0.1 pc 到 600 au 尺度之间的中性物质部分解耦，并暗示 HH 211 中坠落的原恒星包层中存在有效的双极扩散，考虑到这些尺度上的密度，这是主要的非理想磁流体动力学效应。因此，我们的结果可以支持有效双极扩散的情景，从而能够在 HH 211 中形成 20 au 开普勒盘。
To study the transportation of magnetic flux from large to small scales in protostellar sources, we analyzed the Nobeyama 45 m N2H+ (1–0), JCMT 850 μm polarization, and Atacama Large Millimeter/submillimeter Array (ALMA) C18O (2–1) and 1.3 and 0.8 mm (polarized) continuum data of the Class 0 protostar HH 211. The magnetic field strength in the dense core on a 0.1 pc scale was estimated with the single-dish line and polarization data using the Davis–Chandrasekhar–Fermi method, and that in the protostellar envelope on a 600 au scale was estimated from the force balance between the gravity and magnetic field tension by analyzing the gas kinematics and magnetic field structures with the ALMA data. Our analysis suggests that from 0.1 pc–600 au scales, the magnetic field strength increases from 40–107 μG to 0.3–1.2 mG with a scaling relation between the magnetic field strength and density of B ∝ ρ 0.36±0.08, and the mass-to-flux ratio increases from 1.2–3.7 to 9.1–32.3. The increase in the mass-to-flux ratio could suggest that the magnetic field is partially decoupled from the neutral matter between 0.1 pc and 600 au scales, and hint at efficient ambipolar diffusion in the infalling protostellar envelope in HH 211, which is the dominant nonideal magnetohydrodynamic effect considering the density on these scales. Thus, our results could support the scenario of efficient ambipolar diffusion enabling the formation of the 20 au Keplerian disk in HH 211.