磁引力- turbulence中恒星形成核的动网格模拟
Moving mesh simulations of star forming cores in magneto-gravo-turbulence
摘要：
我们银河系中的恒星形成发生在自引力、高度湍流和磁化的分子云中。我们研究了云核继承大尺度磁场形态的条件以及云湍流如何控制该场。我们提出了四个移动网格模拟的超音速，湍流，等温，自引力气体与一系列的磁平均场强度的特点是由阿尔夫维尼克马赫数$\mathcal{M}_{{\rm A}, 0}$，解决前恒星核心的形成从秒差距到几个AU尺度。在我们的模拟与湍流动能密度占主导地位的磁压（$\mathcal{M}_{{\rm A}, 0}>1$），我们发现，崩溃是近似各向同性的$B\proptoρ^{2/3}$，核心的性质是相似的，无论初始的平均场强度，和$100$ AU尺度上的场方向是不相关的平均场。然而，在占主导地位的大尺度磁场（$\mathcal{M}_{{\rm A}, 0}=0.35$）的情况下，崩溃是各向异性的$B\proptoρ^{1/2}$。$\mathcal{M}_{{\rm A}, 0}\sim1$的这种转变预计不会很尖锐，但清楚地表明恒星形成过程中磁场演化的两种不同路径。基于对不同恒星形成区域的观测，我们得出结论，在星际介质中的恒星形成可能发生在这两个区域。随着$\mathcal{M}_{{\rm A}, 0}$的减小，磁场与平均场的相关性扩展到更小的尺度，使得未来的ALMA观测对于约束星际介质的$\mathcal{M}_{{\rm A}, 0}$是有用的。
英文摘要：
Star formation in our Galaxy occurs in molecular clouds that are self-gravitating, highly turbulent, and magnetized. We study the conditions under which cloud cores inherit large-scale magnetic field morphologies and how the field is governed by cloud turbulence. We present four moving-mesh simulations of supersonic, turbulent, isothermal, self-gravitating gas with a range of magnetic mean-field strengths characterized by the Alfvénic Mach number $\mathcal{M}_{{\rm A}, 0}$, resolving pre-stellar core formation from parsec to a few AU scales. In our simulations with the turbulent kinetic energy density dominating over magnetic pressure ($\mathcal{M}_{{\rm A}, 0}>1$), we find that the collapse is approximately isotropic with $B\proptoρ^{2/3}$, core properties are similar regardless of initial mean-field strength, and the field direction on $100$ AU scales is uncorrelated with the mean field. However, in the case of a dominant large-scale magnetic field ($\mathcal{M}_{{\rm A}, 0}=0.35$), the collapse is anisotropic with $B\proptoρ^{1/2}$. This transition at $\mathcal{M}_{{\rm A}, 0}\sim1$ is not expected to be sharp, but clearly signifies two different paths for magnetic field evolution in star formation. Based on observations of different star forming regions, we conclude that star formation in the interstellar medium may occur in both regimes. Magnetic field correlation with the mean-field extends to smaller scales as $\mathcal{M}_{{\rm A}, 0}$ decreases, making future ALMA observations useful for constraining $\mathcal{M}_{{\rm A}, 0}$ of the interstellar medium.
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