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arXiv 0911.1202astro-ph.SRastro-ph.EP
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盘自引力在原恒星和原恒星盘形成中的作用

The role of disc self-gravity in the formation of protostars and protostellar discs

W. K. M. Rice, J. H. Mayo, P. J. Armitage

备注：
11 pages, 8 figures, Accepted for publication in MNRAS
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摘要：

我们使用时间相关的，一维的光盘模型来调查的演变，形成通过分子云核心的崩溃，其中的主要运输机制是自引力的原恒星盘。我们假设这些圆盘进入热平衡状态，Q = 2，角动量输运的强度由圆盘的冷却速率决定。结果表明，这些光盘将达到一个准稳态，持续了一些自由落体的时间，其中大部分的质量在100 au位于10-20 au。内盘中的这种质量堆积可能导致足够高的温度，以便MHD湍流的增长，这可能会迅速排出内盘并导致FU Orionis样的爆发。在我们所有的模拟中，圆盘的内部区域（r < 40 au）对于碎裂是稳定的，而在由具有足够的初始角动量以在这些外部区域沉积足够质量的核心形成的圆盘的外部区域（r > 40 au）中碎裂是可能的。然而，这些外层区域的大量质量表明，碎片化将导致形成亚恒星和恒星质量的伴星，而不是行星质量的物体。虽然质量吸积率在很大程度上与观测结果一致，但大的圆盘质量表明，必须有一种额外的运输机制（如在圆盘上层发生的MRI），以便在观察到的圆盘寿命内排出剩余的圆盘材料。

英文摘要：

We use time-dependent, one-dimensional disc models to investigate the evolution of protostellar discs that form through the collapse of molecular cloud cores and in which the primary transport mechanism is self-gravity. We assume that these discs settle into a state of thermal equilibrium with Q = 2 and that the strength of the angular momentum transport is set by the cooling rate of the disc. The results suggest that these discs will attain a quasi-steady state that persists for a number of free-fall times and in which most of the mass within 100 au is located inside 10-20 au. This pile-up of mass in the inner disc could result in temperatures that are high enough for the growth of MHD turbulence which could rapidly drain the inner disc and lead to FU Orionis-like outbursts. In all our simulations, the inner regions of the discs (r < 40 au) were stable against fragmentation, while fragmentation was possible in the outer regions (r > 40 au) of discs that formed from cores that had enough initial angular momentum to deposit sufficient mass in these outer regions. The large amounts of mass in these outer regions, however, suggests that fragmentation will lead to the formation of sub-stellar and stellar mass companions, rather than planetary mass objects. Although mass accretion rates were largely consistent with observations, the large disc masses suggest that an additional transport mechanism (such as MRI occuring in the upper layers of the disc) must operate in order to drain the remaining disc material within observed disc lifetimes.

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