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arXiv 1302.4901astro-ph.GAastro-ph.SR
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强磁化云核中Turbulence诱导的盘形成

Turbulence-induced disc formation in strongly magnetised cloud cores

D. Seifried, R. Banerjee, R. E. Pudritz, R. S. Klessen

摘要:

我们提出的崩溃模拟强磁化,湍流分子云核心的质量范围从2.6到1000 M太阳,以研究初始条件的影响,最近提出的Seifried等。我们发现,开普勒光盘形成在所有情况下独立的核心质量,湍流的强度,或存在的全球旋转。这些盘在原恒星形成后的几千年内出现,大小为50 - 150 AU,质量在0.05到几个0.1 M太阳之间。在盘的形成过程中,质量流量比保持在开普勒盘形成的临界值10以下。因此,光是磁通损失并不能解释开普勒圆盘的形成。在这样的早期阶段形成旋转支撑的盘是由于无序的磁场结构和由于盘周围的湍流运动,这两个效应降低了经典的磁制动效率。在盘中出现的双星系统主要是通过盘捕获机制而不是通过盘碎片形成的,这在很大程度上被磁场的存在所抑制。

英文摘要:

We present collapse simulations of strongly magnetised, turbulent molecular cloud cores with masses ranging from 2.6 to 1000 M_sun in order to study the influence of the initial conditions on the turbulence-induced disc formation mechanism proposed recently by Seifried et al. 2012. We find that Keplerian discs are formed in all cases independently of the core mass, the strength of turbulence, or the presence of global rotation. The discs appear within a few kyr after the formation of the protostar, are 50 - 150 AU in size, and have masses between 0.05 and a few 0.1 M_sun. During the formation of the discs the mass-to-flux ratio stays well below the critical value of 10 for Keplerian disc formation. Hence, flux-loss alone cannot explain the formation of Keplerian discs. The formation of rotationally supported discs at such early phases is rather due to the disordered magnetic field structure and due to turbulent motions in the surroundings of the discs, two effects lowering the classical magnetic braking efficiency. Binary systems occurring in the discs are mainly formed via the disc capturing mechanism rather than via disc fragmentation, which is largely suppressed by the presence of magnetic fields.

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