磁场和双极扩散调节分子云碎裂的三维模拟
Three-dimensional simulations of molecular cloud fragmentation regulated by magnetic fields and ambipolar diffusion
摘要：
我们采用第一个完全三维模拟研究的作用，磁场和离子中性摩擦调节引力驱动的分子云的碎片。初始亚临界云的核在双极扩散时间内逐渐发展，而初始超临界云的核在动态时间内发展。在最初的亚临界云的情况下，进入核心的速度是亚音速的，而在最初的超临界云的情况下，则存在一个扩展的（\ga 0.1 pc）超音速进入区域。这些结果与以前的二维模拟是一致的。我们还发现，密度（ρ）和磁场强度（B）之间的关系在云的不同空间点的快照与一个单独的核心的演化轨迹相吻合。当密度变大时，两种关系都倾向于B \propto ρ^{0.5}。
英文摘要：
We employ the first fully three-dimensional simulation to study the role of magnetic fields and ion-neutral friction in regulating gravitationally-driven fragmentation of molecular clouds. The cores in an initially subcritical cloud develop gradually over an ambipolar diffusion time while the cores in an initially supercritical cloud develop in a dynamical time. The infall speeds on to cores are subsonic in the case of an initially subcritical cloud, while an extended (\ga 0.1 pc) region of supersonic infall exists in the case of an initially supercritical cloud. These results are consistent with previous two-dimensional simulations. We also found that a snapshot of the relation between density (rho) and the strength of the magnetic field (B) at different spatial points of the cloud coincides with the evolutionary track of an individual core. When the density becomes large, both relations tend to B \propto ρ^{0.5}.
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