Lyα Line Formation in Starbursting Galaxies. II. Extremely Thick, Dustless, and Static H I Media
Lyα Line Formation in Starbursting Galaxies. II. Extremely Thick, Dustless, and Static H I Media
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星爆星系中的 Lyα 线形成 II。
DOI：
10.1086/338497
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发表时间：
2001
期刊：
影响因子：
--
通讯作者：
Hyung
中科院分区：
文献类型：
--
作者：
Sang;Hee;Hyung
通过在蒙特卡罗代码中采用加速方案来跳过大量核心或共振散射，研究了极厚中性氢介质中的 Lyα 线传输。该方案显着减少了计算时间，且不牺牲结果的准确性。我们将此数值方法应用于静态、均匀、无尘且平面平行介质中的 Lyα 传输。考虑了两种类型的光子源；中面源和均匀分布源。出现的轮廓显示双峰和在线中心的吸收谷。我们将我们的结果与之前研究人员得出的分析解决方案进行了比较，并确认这两种解决方案彼此非常一致。我们研究了出现的 Lyα 光子的方向性，发现在稍厚的介质中观察到边缘变亮，而在极厚的介质中出现边缘变暗。值得注意的是，方向性行为遵循电子云中汤姆逊散射辐射的行为，因为 Lyα 翼散射和汤姆逊散射共享相同的瑞利散射相函数。逃逸前机翼散射的平均数量与扩散近似的预测完全一致。构成出射轮廓内部的 Lyα 光子遵循从扩散近似导出的关系。我们简要讨论了我们的结果在星暴星系紫外光谱中看到的 Lyα 宽吸收槽和 P Cygni 型 Lyα 剖面的形成中的应用。
The Lyα line transfer in an extremely thick medium of neutral hydrogen is investigated by adopting an accelerating scheme in our Monte Carlo code to skip a large number of core or resonant scatterings. This scheme reduces computing time significantly, with no sacrifice in the accuracy of the results. We applied this numerical method to the Lyα transfer in a static, uniform, dustless, and plane-parallel medium. Two types of photon sources have been considered; the midplane source and the uniformly distributed sources. The emergent profiles show double peaks and absorption trough at the line center. We compared our results with the analytic solutions derived by previous researchers and confirmed that both solutions are in good agreement with each other. We investigated the directionality of the emergent Lyα photons and found that limb brightening is observed in slightly thick media, while limb darkening appears in extremely thick media. The behavior of the directionality is noted to follow that of the Thomson scattered radiation in electron clouds, because both Lyα wing scattering and Thomson scattering share the same Rayleigh scattering phase function. The mean number of wing scatterings just before escape is in exact agreement with the prediction of the diffusion approximation. The Lyα photons constituting the inner part of the emergent profiles follow the relationship derived from the diffusion approximation. We present a brief discussion on the application of our results to the formation of Lyα broad absorption troughs and P Cygni type Lyα profiles seen in the UV spectra of starburst galaxies.