Taurus分子云中的磁取向速度各向异性
Magnetically Aligned Velocity Anisotropy in the Taurus Molecular Cloud
摘要：
利用计算模拟和分子线观测研究了Taurus分子云的MHD湍流引起的速度各向异性。提出了一种利用星际云光谱成像数据分析速度各向异性程度和角度的新方法。该方法的有效性证明模型观测来自三维速度和密度场的数值MHD模拟，跨越一个范围内的磁场强度。该分析适用于12 CO J=1-0成像的子领域内的金牛座分子云。速度各向异性被识别为在从光学偏振测量导出的平均局部磁场方向的10度内对齐。基于速度各向异性的场强估计值与其他方法的结果一致。当结合金牛座的新柱密度测量时，我们的磁场强度估计表明，云的包络是磁亚临界的。这些观测有利于金牛座云的低密度、亚临界、分子气体基质内的强MHD湍流。
英文摘要：
Velocity anisotropy induced by MHD turbulence is investigated using computational simulations and molecular line observations of the Taurus molecular cloud. A new analysis method is presented to evaluate the degree and angle of velocity anisotropy using spectroscopic imaging data of interstellar clouds. The efficacy of this method is demonstrated on model observations derived from three dimensional velocity and density fields from the set of numerical MHD simulations that span a range of magnetic field strengths. The analysis is applied to 12CO J=1-0 imaging of a sub-field within the Taurus molecular cloud. Velocity anisotropy is identified that is aligned within 10 degrees of the mean local magnetic field direction derived from optical polarization measurements. Estimated values of the field strength based on velocity anisotropy are consistent with results from other methods. When combined with new column density measurements for Taurus, our magnetic field strength estimate indicates that the envelope of the cloud is magnetically subcritical. These observations favor strong MHD turbulence within the low density, sub-critical, molecular gas substrate of the Taurus cloud.
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