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THE FORMATION OF SELF-GRAVITATING CORES IN TURBULENT MAGNETIZED CLOUDS

机译:湍动磁化云中自重心的形成

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We use ZEUS-MP to perform high-resolution, three-dimensional, super-Alfvenic turbulent simulations in order to investigate the role of magnetic fields in self-gravitating core formation within turbulent molecular clouds. Statistical properties of our super-Alfvenic model without gravity agree with previous similar studies. Including self-gravity, our models give the following results. They are consistent with the turbulent fragmentation prediction of the core mass distribution of Padoan & Nordlund. They also confirm that local gravitational collapse is not prevented by magnetohydrodynamic waves driven by turbulent flows, even when the turbulent Jeans mass exceeds the mass in the simulation volume. Comparison of results between 256~3 and 512~3 zone simulations reveals convergence in the collapse rate. Analysis of self-gravitating cores formed in the simulation shows the following: (1) All cores formed are magnetically supercritical by at least an order of magnitude. (2) A power-law relation between central magnetic field strength and density B_c ∝ ρ_c~(1/2) is observed despite the cores being strongly supercritical. (3) Specific angular momentum j ∝ R~(3/2) for cores with radius R. (4) Most cores are prolate and triaxial in shape, in agreement with the results of Gammie and coworkers. We find a weak correlation between the minor axis of the core and the local magnetic field in our simulation at late times, different from the uncorrelated results reported by Gammie and coworkers. The core shape analysis and the power-law relationship between core mass and radius M ∝ R~(2.75) suggest the formation of some highly flattened cores. We identified 12 cloud cores with disklike appearance at a later stage of our high-resolution simulation. Instead of being tidally truncated or disrupted, the core disks survive and flourish while undergoing strong interactions. We discuss the physical properties of these disklike cores under the constraints of resolution limits.
机译:我们使用ZEUS-MP进行高分辨率,三维,超Alfvenic湍流模拟,以研究磁场在湍流分子云中自重岩心形成中的作用。我们没有引力的超级Alfvenic模型的统计性质与以前的类似研究一致。包括自重在内,我们的模型得出以下结果。它们与Padoan&Nordlund核心质量分布的湍流破碎预测一致。他们还证实,即使湍流的Jeans质量超过了模拟体积中的质量,湍流驱动的磁流体动力学波也无法防止局部重力塌陷。 256〜3和512〜3区模拟结果的比较表明,坍塌率具有收敛性。在仿真中形成的自重磁芯的分析显示如下:(1)形成的所有磁芯在磁性上都是超临界的,至少一个数量级。 (2)观察到中心磁场强度与密度B_c ∝ρ_c〜(1/2)之间的幂律关系,尽管铁心是超临界的。 (3)半径为R的铁心的比角动量j ∝ R〜(3/2)。(4)大多数铁心呈长轴形和三轴形,与Gammie及其同事的结果一致。在后期的仿真中,我们发现磁芯的短轴与局部磁场之间的相关性较弱,这与Gammie和同事报告的不相关结果不同。铁心形状分析和铁心质量与半径M ∝ R〜(2.75)之间的幂律关系表明形成了一些高度扁平的铁心。在高分辨率模拟的后期,我们确定了12个具有磁盘状外观的云核心。核心磁盘没有被潮汐般的截断或破坏,而是在经受强相互作用的同时生存并繁荣发展。我们讨论在分辨率限制的约束下这些磁盘状核心的物理属性。

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