论文标题
通过两相原子气的冲击压缩形成的磁化分子云中致密团块的通用性能
Universal Properties of Dense Clumps in Magnetized Molecular Clouds Formed through Shock Compression of Two-phase Atomic Gases
论文作者
论文摘要
我们通过使用三维磁水动力学模拟，包括非平衡化学反应，加热/冷却过程以及通过改变碰撞速度$ v_0 $以及磁场和碰撞流之间的角度$θ$来研究来自原子气的分子云的形成。我们发现，密集气体形成的效率取决于$θ$。对于小$θ$，各向异性超级alfvénic湍流延迟了重力不稳定的团块的形成。 $θ$的增加形成了累积气体的冲击放大磁场，从而使突出的丝状结构产生。我们进一步研究了用不同密度阈值鉴定的致密团块的统计特性。密度较低的致密团块的统计特性取决于$ v_0 $和$θ$，因为它们的属性是从分子云的全局湍流结构继承的。相比之下，较密集的统计特性似乎具有渐近的通用统计特性，这不取决于碰撞流的特性。内部速度分散剂接近亚音速和等离子体$β$成为统一的顺序。我们开发了病毒参数的分析公式，该公式可以很好地重现模拟结果。该特性可能是恒星初始质量功能普遍性的原因之一。
We investigate the formation of molecular clouds from atomic gas by using three-dimensional magnetohydrodynamical simulations,including non-equilibrium chemical reactions, heating/cooling processes, and self-gravity by changing the collision speed $V_0$ and the angle $θ$ between the magnetic field and colliding flow. We found that the efficiency of the dense gas formation depends on $θ$. For small $θ$, anisotropic super-Alfvénic turbulence delays the formation of gravitationally unstable clumps. An increase in $θ$ develops shock-amplified magnetic fields along which the gas is accumulated, making prominent filamentary structures. We further investigate the statistical properties of dense clumps identified with different density thresholds. The statistical properties of the dense clumps with lower densities depend on $V_0$ and $θ$ because their properties are inherited from the global turbulence structure of the molecular clouds. By contrast, denser clumps appear to have asymptotic universal statistical properties, which do not depend on the properties of the colliding flow significantly. The internal velocity dispersions approach subsonic and plasma $β$ becomes order of unity. We develop an analytic formula of the virial parameter which reproduces the simulation results reasonably well. This property may be one of the reasons for the universality of the initial mass function of stars.
