Magnetic fields at the onset of high-mass star formation
Magnetic fields at the onset of high-mass star formation
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DOI：
10.1051/0004-6361/201732378
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发表时间：
2018-01
影响因子：
6.5
通讯作者：
H. Beuther;J. D. Soler;W. Vlemmings;H. Linz;T. Henning;R. Kuiper;R. Rao;Rowan J. Smith;Takeshi Sakai;K. Johnston;Andrew Walsh;S. Feng
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文献类型：
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作者：
H. Beuther;J. D. Soler;W. Vlemmings;H. Linz;T. Henning;R. Kuiper;R. Rao;Rowan J. Smith;Takeshi Sakai;K. Johnston;Andrew Walsh;S. Feng
上下文磁场在星星形成初期与早期碎裂和坍缩过程有关的重要性，今天基本上还没有被探索。目标。我们想了解大质量星星形成的最早演化阶段的磁场特性。方法.阿塔卡马大型毫米波阵列在1.3毫米波长的全偏振模式下用于研究偏振发射，并使用该模式研究大质量无星区域IRDC 18310 - 4的磁场形态和强度。结果在该区域的四个子核中清楚地检测到偏振发射;一般来说，它显示出平滑的分布，也沿着细长的核。通过Davis-Krasekhar-Fermi方法估计磁场强度，并进行结构函数分析，我们发现在~0.3 - 5.3 mG之间有很大的磁场强度。将这些数据与谱线观测结果进行比较，磁能量与磁能的比值很低，这表明湍流对气体团的稳定性没有显着贡献。质量通量比在临界值1.0附近（取决于柱密度）表明该区域开始塌陷，这与之前对该区域的谱线分析一致。结论.虽然这个高质量区域正在坍缩，因此处于星星形成的边缘，但高磁场值和平滑的空间结构表明磁场对碎裂和坍缩过程很重要。这个单一的案例研究只能是星星形成初期磁场的更大样本研究的起点。
Context. The importance of magnetic fields at the onset of star formation related to the early fragmentation and collapse processes is largely unexplored today. Aims. We want to understand the magnetic field properties at the earliest evolutionary stages of high-mass star formation. Methods. The Atacama Large Millimeter Array is used at 1.3 mm wavelength in full polarization mode to study the polarized emission, and, using this, the magnetic field morphologies and strengths of the high-mass starless region IRDC 18310-4. Results. Polarized emission is clearly detected in four sub-cores of the region; in general it shows a smooth distribution, also along elongated cores. Estimating the magnetic field strength via the Davis-Chandrasekhar-Fermi method and following a structure function analysis, we find comparably large magnetic field strengths between ~0.3–5.3 mG. Comparing the data to spectral line observations, the turbulent-to-magnetic energy ratio is low, indicating that turbulence does not significantly contribute to the stability of the gas clump. A mass-to-flux ratio around the critical value 1.0 – depending on column density – indicates that the region starts to collapse, which is consistent with the previous spectral line analysis of the region. Conclusions. While this high-mass region is collapsing and thus at the verge of star formation, the high magnetic field values and the smooth spatial structure indicate that the magnetic field is important for the fragmentation and collapse process. This single case study can only be the starting point for larger sample studies of magnetic fields at the onset of star formation.