Dynamical expansion of ionization and dissociation front around a massive star. II. On the generality of triggered star formation
Dynamical expansion of ionization and dissociation front around a massive star. II. On the generality of triggered star formation
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DOI：
10.1086/504789
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发表时间：
2006-07-20
影响因子：
4.9
通讯作者：
Inutsuka, Shu-Ichiro
中科院分区：
文献类型：
--
作者：
Hosokawa, Takashi;Inutsuka, Shu-Ichiro
我们分析了H II区、光解区和横扫壳的动态扩展，求解了随时间流体动力学代码中的紫外和远紫外辐射传递以及热化学过程。在前人的基础上，我们研究了不同环境数密度和中心恒星的时间演化。我们的计算表明，在不同参数的模型中，基本进化在质量上是相似的。分子气体最终聚集在壳层中，壳层的引力破碎是一般预期的。用解析标度关系可以很好地理解模型之间的定量差异。壳体的详细物理化学结构主要由入射远紫外通量和壳体的柱密度决定，它们也遵循标度关系。壳体破碎时间和聚集的分子气体质量对环境数密度敏感。在低密度的情况下，壳破碎发生的时间更长，积累的分子气体比高密度的情况下质量更大。不同中心恒星之间的变化比较温和。在M-* = 12-101 M-圆点范围内，不同恒星的壳层破碎时间相差数倍。根据我们的数值结果，我们得出结论，如果周围分子物质的质量足够大，膨胀的H II区域应该是分子云中恒星形成的有效触发器。
We analyze the dynamical expansion of the H II region, photodissociation region, and the swept-up shell, solving the UV and far-UV radiative transfer and the thermal and chemical processes in the time-dependent hydrodynamics code. Following our previous paper, we investigate the time evolutions with various ambient number densities and central stars. Our calculations show that basic evolution is qualitatively similar among our models with different parameters. The molecular gas is finally accumulated in the shell, and the gravitational fragmentation of the shell is generally expected. The quantitative differences among models are well understood with analytic scaling relations. The detailed physical and chemical structure of the shell is mainly determined by the incident far-UV flux and the column density of the shell, which also follow the scaling relations. The time of shell fragmentation and the mass of the gathered molecular gas are sensitive to the ambient number density. In the case of a low density, the shell fragmentation occurs over a longer timescale, and the accumulated molecular gas is more massive than in the case of a high density. The variations with different central stars are more moderate. The time of the shell fragmentation differs by a factor of several with the various stars of M-* = 12-101 M-circle dot. According to our numerical results, we conclude that the expanding H II region should be an efficient trigger for star formation in molecular clouds if the mass of the ambient molecular material is large enough.