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首页> 外文期刊>The Astrophysical journal >FORMATION AND COLLAPSE OF NONAXISYMMETRIC PROTOSTELLAR CORES IN PLANAR MAGNETIC INTERSTELLAR CLOUDS: FORMULATION OF THE PROBLEM AND LINEAR ANALYSIS
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FORMATION AND COLLAPSE OF NONAXISYMMETRIC PROTOSTELLAR CORES IN PLANAR MAGNETIC INTERSTELLAR CLOUDS: FORMULATION OF THE PROBLEM AND LINEAR ANALYSIS

机译：平面磁性星际云中非对称对称恒星孔的形成与塌陷：问题的形成与线性分析

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摘要

We formulate the problem of the formation and collapse of nonaxisymmetric protostellar cores in weakly ionized, self-gravitating, magnetic molecular clouds. In our formulation, molecular clouds are approximated as isothermal, thin (but with finite thickness) sheets. We present the governing dynamical equations for the multifluid system of neutral gas and ions, including ambipolar diffusion, and also a self-consistent treatment of thermal pressure, gravitational, and magnetic (pressure and tension) forces. The dimensionless free parameters characterizing model clouds are discussed. The response of cloud models to linear perturbations is also examined, with particular emphasis on length- and timescales for the growth of gravitational instability in magnetically subcritical and supercritical clouds. We investigate their dependence on a cloud's initial mass-to-magnetic-flux ratio μ_0 (normalized to the critical value for collapse), the dimensionless initial neutral-ion collision time τ_(ni,0), and also the relative external pressure exerted on a model cloud P_(ext). Among our results, we find that nearly critical model clouds have significantly larger characteristic instability length scales than do more distinctly sub- or supercritical models. Another result is that the effect of a greater external pressure is to reduce the critical length scale for instability. Numerical simulations showing the evolution of model clouds during the linear regime of evolution are also presented, and compared to the results of the dispersion analysis. They are found to be in agreement with the dispersion results, and confirm the dependence of the characteristic length- and timescales on parameters such as μ_0 and P_(ext).
机译：我们提出了在弱电离的，自重的磁性分子云中非轴对称的原星核形成和坍塌的问题。在我们的公式中，分子云近似为等温，薄（但厚度有限）的薄片。我们提出了中性气体和离子的多流体系统的主导动力学方程，包括双极性扩散，还对热压力，重力和磁力（压力和张力）进行了自洽处理。讨论了表征模型云的无量纲自由参数。还检查了云模型对线性摄动的响应，特别强调了在磁次临界和超临界云中重力不稳定性增长的长度和时间尺度。我们研究了它们对云的初始质量与磁通量比率μ_0（归一化为坍塌的临界值），无量纲的初始中性离子碰撞时间τ_（ni，0）以及施加在云上的相对外部压力的依赖性。模型云P_（ext）。在我们的结果中，我们发现，比更分明的亚临界或超临界模型，近临界模型云具有更大的特征不稳定性长度尺度。另一个结果是，更大的外部压力会降低不稳定性的临界长度范围。还给出了数值模拟，显示了线性演化过程中模型云的演化，并与色散分析的结果进行了比较。发现它们与色散结果一致，并证实了特征长度和时标对诸如μ_0和P_（ext）之类的参数的依赖性。

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