博克球中的大尺度磁场
Large-scale magnetic fields in Bok globules
摘要：
背景：磁场在恒星形成过程中的作用是一个有争议的问题。特别是，没有明确的观测证据表明，在分子云的初始坍缩过程中，磁场会产生普遍的影响。目的：我们的目标是研究磁场及其对低质量恒星形成区大范围空间尺度的影响。方法：我们通过光学和近红外偏振测量追踪博克球局部环境中10^3-10^5 AU尺度的大尺度磁场结构，并将这些测量与现有的亚毫米测量相结合，从而表征10^2-10^3 AU尺度的小尺度磁场结构。结果如下：这是第一次，我们提出的偏振观测在光学和近红外的三个博克球B335，CB 68和CB 54，结合档案观测在亚毫米和光学。在光学和近红外波段，我们发现三个球状体都有明显的偏振信号（P>= 2%，P/sigma（P）>3）。此外，我们检测到B335和CB 68在10^2-10^3 AU到10^3-10^4 AU尺度上的结构之间的联系。此外，对于CB 54，我们在~10^5 AU的尺度上追踪了有序的偏振矢量。我们确定了一个磁场方向，在CB 54的情况下与CO流出对齐，但几乎垂直于CB 68的CO流出。对于B335，我们发现磁场从内核到外部区域朝向流出方向的变化。结论：我们发现强烈对齐的极化矢量，表明占主导地位的磁场在很大范围的空间尺度。
英文摘要：
Context: The role of magnetic fields in the star formation process is a contentious matter of debate. In particular, no clear observational proof exists of a general influence by magnetic fields during the initial collapse of molecular clouds. Aims: Our aim is to examine magnetic fields and their influence on a wide range of spatial scales in low-mass star-forming regions. Method: We trace the large-scale magnetic field structure on scales of 10^3-10^5 AU in the local environment of Bok globules through optical and near-infrared polarimetry and combine these measurements with existing submillimeter measurements, thereby characterizing the small-scale magnetic field structure on scales of 10^2-10^3 AU. Results: For the first time, we present polarimetric observations in the optical and near-infrared of the three Bok globules B335, CB68, and CB54, combined with archival observations in the submillimeter and the optical. We find a significant polarization signal (P>=2%, P/sigma(P)>3) in the optical and near-infrared for all three globules. Additionally, we detect a connection between the structure on scales of 10^2-10^3 AU to 10^3-10^4 AU for both B335 and CB68. Furthermore, for CB54, we trace ordered polarization vectors on scales of ~10^5 AU. We determine a magnetic field orientation that is aligned with the CO outflow in the case of CB54, but nearly perpendicular to the CO outflow for CB68. For B335 we find a change in the magnetic field oriented toward the outflow direction, from the inner core to the outer regions. Conclusion: We find strongly aligned polarization vectors that indicate dominant magnetic fields on a wide range of spatial scales.
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