MEASURING THE ALFVÉNIC NATURE OF THE INTERSTELLAR MEDIUM: VELOCITY ANISOTROPY REVISITED
MEASURING THE ALFVÉNIC NATURE OF THE INTERSTELLAR MEDIUM: VELOCITY ANISOTROPY REVISITED
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测量星际介质的大气性质：重新审视速度各向异性
DOI：
10.1088/0004-637x/790/2/130
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发表时间：
2014
期刊：
影响因子：
--
通讯作者：
A. Esquivel
中科院分区：
文献类型：
--
作者：
B. Burkhart;A. Lazarian;I. Leão;J. R. D. Medeiros;A. Esquivel
星际介质（ISM）的动力学受到湍流的强烈影响，湍流在磁场存在下表现出增加的各向异性。我们扩展了Esquivel和Lazarian方法，利用位置-位置-速度图中速度质心数据的结构函数各向异性来估计Alfvén马赫数。我们利用三维磁流体动力学模拟充分发展的湍流，具有大范围的音速和Alfvénic马赫数，以产生速度质心的综合观测与观测特性，如热加宽，云边界，噪声和一氧化碳的辐射传输效应。此外，我们研究了Esquivel和Lazarian中发现的各向异性-Alfvén马赫数依赖性在位置-位置-速度立方体的二阶矩或使用不同表达式计算速度质心时可能会发生的变化。我们发现各向异性的程度主要与磁场强度有关（即，Alfvén马赫数）和视线方向，对音速马赫数有次要影响。如果视线平行于平均场方向达0.45度，则速度质心各向异性不足以突出以区分不同的Alfvénic区域。观察到的各向异性不会受到辐射传输的强烈影响，尽管未来的研究应该包括对不透明度效应的额外测试。这些结果开辟了可能性研究的磁性ISM使用统计方法，除了现有的观测技术。
The dynamics of the interstellar medium (ISM) are strongly affected by turbulence, which shows increased anisotropy in the presence of a magnetic field. We expand upon the Esquivel & Lazarian method to estimate the Alfvén Mach number using the structure function anisotropy in velocity centroid data from Position–Position–Velocity maps. We utilize three-dimensional magnetohydrodynamic simulations of fully developed turbulence, with a large range of sonic and Alfvénic Mach numbers, to produce synthetic observations of velocity centroids with observational characteristics such as thermal broadening, cloud boundaries, noise, and radiative transfer effects of carbon monoxide. In addition, we investigate how the resulting anisotropy-Alfvén Mach number dependency found in Esquivel & Lazarian might change when taking the second moment of the Position–Position–Velocity cube or when using different expressions to calculate the velocity centroids. We find that the degree of anisotropy is related primarily to the magnetic field strength (i.e., Alfvén Mach number) and the line-of-sight orientation, with a secondary effect on sonic Mach number. If the line of sight is parallel to up to ≈45 deg off of the mean field direction, the velocity centroid anisotropy is not prominent enough to distinguish different Alfvénic regimes. The observed anisotropy is not strongly affected by including radiative transfer, although future studies should include additional tests for opacity effects. These results open up the possibility of studying the magnetic nature of the ISM using statistical methods in addition to existing observational techniques.
DOI：
10.1088/0004-637x/771/2/123
发表时间：
2013
期刊：
The Astrophysical Journal
影响因子：
--
作者：
Burkhart;Lazarian;Ossenkopf;Stutzki
通讯作者：
Stutzki