GRAVITATIONAL FRAGMENTATION OF EXPANDING SHELLS. I. LINEAR ANALYSIS
GRAVITATIONAL FRAGMENTATION OF EXPANDING SHELLS. I. LINEAR ANALYSIS
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DOI：
10.1088/0004-637x/733/1/16
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发表时间：
2011-03
期刊：
影响因子：
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通讯作者：
K. Iwasaki;S. Inutsuka;T. Tsuribe
中科院分区：
文献类型：
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作者：
K. Iwasaki;S. Inutsuka;T. Tsuribe
我们对H区膨胀驱动的膨胀壳进行了线性微扰分析。假定周围的气体是均匀的。作为非扰动状态，我们开发了一种半解析方法来推导密度分布在厚度上的时间演化。结果表明，密度剖面的时间演化可划分为减速主导、中间主导和自重力主导三个演化阶段。随着壳体的膨胀，密度峰值相对地从激波前缘向接触不连续方向移动。考虑到由半解析方法得到的非对称密度分布，我们进行了线性分析，并对激波前沿和接触不连续施加了边界条件，而忽略了壳的演化效应。研究发现，与以往基于薄壳近似的研究相比，生长速率有所提高。这是由于接触不连续和不对称密度分布的边界效应，在以前的工作中没有考虑到。
We perform a linear perturbation analysis of expanding shells driven by expansions of H ii regions. The ambient gas is assumed to be uniform. As an unperturbed state, we develop a semi-analytic method for deriving the time evolution of the density profile across the thickness. It is found that the time evolution of the density profile can be divided into three evolutionary phases: deceleration-dominated, intermediate, and self-gravity-dominated phases. The density peak moves relatively from the shock front to the contact discontinuity as the shell expands. We perform a linear analysis taking into account the asymmetric density profile obtained by the semi-analytic method, and imposing the boundary conditions for the shock front and the contact discontinuity while the evolutionary effect of the shell is neglected. It is found that the growth rate is enhanced compared with previous studies based on the thin-shell approximation. This is due to the boundary effect of the contact discontinuity and asymmetric density profile that were not taken into account in previous works.