定向Lya等效升压I。团簇的球对称分布
Directional Lya equivalent boosting I. Spherically symmetric distributions of clumps
摘要：
我们量化了Lyman- $α$（Ly $α$）和非电离紫外连续光子从多相介质中的逃逸分数的方向依赖性，并研究了Ly $α$等效宽度（EW）是否存在方向增强。我们的多相介质由球对称分布的冷，尘埃团块嵌入在一个热的无尘介质。我们关注Laursen等人（2013）分析的三个模型。我们发现，对于一个Ly $α$和紫外连续点源，它是可能的，找到一个EW的提升$b(θ,ϕ) > 5 \bar{b}$在百分之几的视线，其中$\bar{b}$表示在所有光子的平均提升。对于空间扩展的源，当紫外线发射区域的大小超过冷尘埃团之间的平均距离时，这种方向依赖性很快消失。我们的分析表明，定向EW助推可以发生，这主要是由减少逃逸分数的UV光子（这会引起UV-连续“阴影”），并由于增强的LY $α$逃逸分数（或光束），在某些方向。
英文摘要：
We quantify the directional dependence of the escape fraction of Lyman-$α$ (Ly$α$) and non-ionising UV-continuum photons from a multiphase medium, and investigate whether there exist directional enhancements in the Ly$α$ equivalent width (EW). Our multiphase medium consists of spherically symmetric distributions of cold, dusty clumps embedded within a hot dust-free medium. We focus on three models from the analysis presented by Laursen et al. (2013). We find that for a Ly$α$ and UV-continuum point source, it is possible to find an EW boost $b(θ,ϕ) > 5 \bar{b}$ in a few per cent of sight lines, where $\bar{b}$ denotes the boost averaged over all photons. For spatially extended sources this directional dependence vanishes quickly when the size of the UV emitting region exceeds the mean distance between cold dusty clumps. Our analysis suggests that directional EW boosting can occur, and that this is mostly driven by reduced escape fractions of UV photons (which gives rise to UV-continuum `shadows'), and less due to an enhanced Ly$α$ escape fraction (or beaming), in certain directions.
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