Intrinsic, Observed, and Retrieved Properties of Interstellar Turbulence
Intrinsic, Observed, and Retrieved Properties of Interstellar Turbulence
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星际湍流的内在、观测和检索特性
DOI：
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发表时间：
2003
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通讯作者：
B. Pichardo
中科院分区：
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作者：
C. Brunt;M. Heyer;E. Vázquez;B. Pichardo
我们生成合成观测的三维，自引力MHD模拟的星际介质（ISM），以评估主成分分析（PCA）的能力，以测量分子云的湍流速度波动的尺度依赖性。将观测得到的线剖面速度变化率δv和空间变化率L（其中δv <$Lα）的耦合特征标度的标度指数α与MHD速度场的本征标度指数进行了比较。我们确定PCA操作的近似结构函数顺序，以便验证先前建立的PCA方法的校准。我们还分析了投影速度线质心场的统计特性，包括间歇性速度波动，密度不均匀性和不透明度的影响，并检查投影的二维统计的内在三维统计的关系。使用PCA，我们推断陡峭的三维能谱的分子ISM，一般比可以占柯尔莫哥洛夫湍流，甚至可能是冲击为主的湍流。
We generate synthetic observations of three-dimensional, self-gravitating MHD simulations of the interstellar medium (ISM) to evaluate the ability of principal component analysis (PCA) to measure the scale dependence of turbulent velocity fluctuations in molecular clouds. Scaling exponents, α, observationally obtained from the coupled characteristic scales for line profile variability in velocity, δv, and in space, L, where δv ∝ Lα, are compared with the intrinsic scaling exponents of the MHD velocity fields. We determine the approximate structure function order at which PCA operates in order to then verify a previously established calibration of the PCA method. We also analyze the statistical properties of projected velocity line centroid fields, including effects of intermittent velocity fluctuations, density inhomogeneity, and opacity, and examine the relationship of the projected two-dimensional statistics to the intrinsic three-dimensional statistics. Using PCA, we infer steep three-dimensional energy spectra in the molecular ISM, generally steeper than can be accounted for by Kolmogorov turbulence or possibly even shock-dominated turbulence.