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首页> 外文期刊>PASJ: Publications of the Astronomical Society of Japan >Formation of Galactic Center Magnetic Loops
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Formation of Galactic Center Magnetic Loops

机译：银河系中心磁环的形成

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A survey of the molecular clouds in the Galaxy with the NANTEN mm telescope has discovered molecular loops in the galactic center region. They show monotonic gradients of the line-of-sight velocity along the loops and large velocity dispersions towards their foot-points. It is suggested that these loops can be explained in terms of a buoyant rise of magnetic loops due to a Parker instability. We carried out global three-dimensional magneto-hydrodynamic simulations of the gas disk in the galactic center. The gravitational potential was approximated by an axisymmetric potential proposed by Miyamoto and Nagai (1975, PASJ, 27, 533). At the initial state, we assumed a warm (～10~4 K) gas torus threaded by azimuthal magnetic fields. Self-gravity and radiative cooling of the gas were ignored. We found that buoyantly rising magnetic loops are formed above the differentially rotating, magnetically turbulent disk. By analyzing the results of global MHD simulations, we identified individual loops, about 180 in the upper half of the disk, and studied their statistical properties, such as their length, width, height, and velocity distributions along the loops. The typical length and height of a loop are 1 kpc and 200 pc, respectively. The line-of-sight velocity changes linearly along a loop, and shows large dispersions around the foot-points. Numerical results indicate that loops emerge preferentially from the region where the magnetic pressure is large. We argue that these properties are consistent with those of molecular loops discovered by NANTEN.
机译：使用NANTEN毫米望远镜对银河系中的分子云进行调查后，发现银河系中心区域存在分子环。它们显示了沿环路的视线速度的单调梯度，以及朝向其脚点的大速度色散。建议可以用帕克不稳定性引起的磁环的上升来解释这些环。我们对银河系中心气盘进行了全球三维磁流体动力学模拟。重力势能由宫本和长井（1975，PASJ，27，533）提出的轴对称势来近似。在初始状态下，我们假设由方位角磁场穿过的温暖的（约10〜4 K）气体环面。气体的自重和辐射冷却被忽略。我们发现，在差速旋转的磁湍流盘上方形成了上升的磁环。通过分析全局MHD仿真的结果，我们确定了单个环，在磁盘的上半部大约有180个，并研究了它们的统计属性，例如沿环的长度，宽度，高度和速度分布。回路的典型长度和高度分别为1 kpc和200 pc。视线速度沿环路线性变化，并且在脚点周围显示出较大的分散。数值结果表明，回路优先从磁压大的区域出现。我们认为这些性质与NANTEN发现的分子环的性质是一致的。

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