Tracing Multi-scale Magnetic Field Structure Using Multiple Chemical Tracers in Giant Molecular Clouds
Tracing Multi-scale Magnetic Field Structure Using Multiple Chemical Tracers in Giant Molecular Clouds
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DOI：
10.3847/1538-4357/ab41f2
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发表时间：
2019-04
期刊：
影响因子：
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通讯作者：
Yue Hu;K. Yuen;A. Lazarian;L. Fissel;Paul Jones;Maria R. Cunningham
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作者：
Yue Hu;K. Yuen;A. Lazarian;L. Fissel;Paul Jones;Maria R. Cunningham
在巨大的分子云中探测磁场通常具有挑战性。幸运的是，最近的模拟表明，分析速度梯度（速度梯度技术; VGT）可以用来映射出磁场形态的不同物理层的分子云时，适用于CO同位素具有不同的光学深度。在这里，我们测试了VGT在重建分子云船帆座C的磁场结构方面的有效性，采用了七种具有不同光学深度的化学示踪剂，即，12 CO、13 CO、C18 O、CS、HNC、HCO+和HCN。我们的研究结果表明，使用这些不同的分子示踪剂从速度梯度推断的磁场形态和从BLASTPol极化观测推断的磁场形态之间具有良好的对应关系。我们还探讨了使用多种化学示踪剂的速度梯度的组合来解释分子云中的磁场结构的可能性。我们搜索的速度梯度和磁场的对齐的引力坍缩的签名，并得出结论，坍缩区域构成的云的一小部分。
Probing magnetic fields in giant molecular clouds is often challenging. Fortunately, recent simulations show that analysis of velocity gradients (the velocity gradient technique; VGT) can be used to map out the magnetic field morphology of different physical layers within molecular clouds when applied to CO isotopologues with different optical depths. Here, we test the effectiveness of the VGT in reconstructing the magnetic field structure of the molecular cloud Vela C, employing seven chemical tracers that have different optical depths, i.e., 12CO, 13CO, C18O, CS, HNC, HCO+, and HCN. Our results show good correspondence between the magnetic field morphology inferred from velocity gradients using these different molecular tracers and the magnetic field morphology inferred from BLASTPol polarization observations. We also explore the possibility of using a combination of velocity gradients for multiple chemical tracers to explain the structure of the magnetic field in molecular clouds. We search for signatures of gravitational collapse in the alignment of the velocity gradients and magnetic field and conclude that collapsing regions constitute a small fraction of the cloud.