Evolution of prolate molecular clouds at H II boundaries - I. Formation of fragment-core structures
Evolution of prolate molecular clouds at H II boundaries - I. Formation of fragment-core structures
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H II 边界长形分子云的演化 - I. 碎片核心结构的形成
DOI：
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发表时间：
2014
期刊：
影响因子：
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通讯作者：
S. Goodwin
中科院分区：
文献类型：
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作者：
T. Kinnear;J. Miao;G. White;S. Goodwin
用光滑粒子流体力学方法研究了在H - II边界处的扩展云的演化。在我们的研究中，长形分子云的半长轴垂直于平平行电离极紫外（EUV）通量的辐射方向。对三种高质量长形云的模拟表明，EUV辐射可以触发嵌入最终线性结构的独特高密度核心形成。这与之前的研究结果形成了对比，在之前的研究中，只使用了各向同性的远紫外星际背景通量。对一组质量相等但初始密度和几何形状不同的长形云的系统研究发现，随着长形云的初始条件和EUV辐射通量的强度的变化，长形云的核心在最终线性结构上的分布发生了变化。根据电离辐射穿透深度dEUV（物理电离辐射穿透深度与云的小轴的比值）的值，这些高度凝聚的核要么分散在最终线性结构的整个长度上，要么在两个焦点上形成两组高密度核。对高密度核的总质量和核形成时间的数据分析发现，在所研究的物理环境中，在电离穿透深度较浅、主-小轴比中等的长形云中，EUV辐射触发恒星形成效率的潜力更高。最后，提出了在H II边界观测到的各种碎片核结构可能是电离辐射与不同初始几何和物理条件的预先存在的延伸云相互作用的结果。
The evolution of a prolate cloud at an H II boundary is investigated using smoothed particle hydrodynamics. The prolate molecular clouds in our investigation are set with their semi-major axis perpendicular to the radiative direction of a plane-parallel ionizing extreme ultraviolet (EUV) flux. Simulations on three high-mass prolate clouds reveal that EUV radiation can trigger distinctive high-density core formation embedded in a final linear structure. This contrasts with results of the previous work in which only an isotropic far-ultraviolet interstellar background flux was applied. A systematic investigation on a group of prolate clouds of equal mass but different initial densities and geometric shapes finds that the distribution of the cores over the final linear structure changes with the initial conditions of the prolate cloud and the strength of the EUV radiation flux. These highly condensed cores may either scatter over the full length of the final linear structure or form two groups of high-density cores at two foci, depending on the value of the ionizing radiation penetration depth dEUV, the ratio of the physical ionizing radiation penetration depth to the minor axis of the cloud. Data analysis on the total mass of the high-density cores and the core formation time finds that the potential for EUV radiation triggered star formation efficiency is higher in prolate clouds with shallow ionization penetration depth and intermediate major-to-minor axial ratio, for the physical environments investigated. Finally, it is suggested that the various fragment-core structures observed at H II boundaries may result from the interaction between ionizing radiation and pre-existing prolate clouds of different initial geometrical and physical conditions.