用Shapefinder和渗滤分析研究再电离过程中HI等密度表面的形态
Studying the morphology of HI isodensity surfaces during reionization using Shapefinders and percolation analysis
摘要：
Minkowski泛函和Shapefinder通过确定大尺度结构的拓扑结构和形态结构来揭示其连通性。我们使用一个复杂的代码，SURFGEN 2，测量的Minkowski泛函和Shapefinder的个别集群的集群表面建模使用的“行军立方33”三角剖分算法。在本文中，我们研究了模拟中性氢（HI）密度场的形态使用Shapefinder在不同阶段的再电离的偏移集方法。伴随着Shapefinders，我们还采用了“最大聚类统计”（LCS）来理解渗流过程。逾渗曲线表明，在HI场的非高斯性增加的再电离的进展。HI过密和欠密偏移集中的大星系团具有相似的“厚度”（$T$）和“宽度”（$B$）值，但它们的第三个Shapefinder --“长度”（$L$）--几乎与它们的体积成正比。在HI过密和欠密段的大团簇都绝大多数是连续的。可以使用前两个Shapefinder的乘积$T \times B$来估计非线性簇的“横截面”。因此，在渗流开始时，大团簇的截面随体积变化不大，它们的大小仅在长度方面有所不同。这一功能出现更生动地在HI过密区域比在undersense地区，是更明显的，在较低的红移对应于一个先进的再电离阶段。
英文摘要：
Minkowski functionals and Shapefinders shed light on the connectedness of large-scale structure by determining its topology and morphology. We use a sophisticated code, SURFGEN2, to measure the Minkowski functionals and Shapefinders of individual clusters by modelling cluster surfaces using the 'Marching Cube 33' triangulation algorithm. In this paper, we study the morphology of simulated neutral hydrogen (HI) density fields using Shapefinders at various stages of reionization from the excursion set approach. Accompanying the Shapefinders, we also employ the 'largest cluster statistic' (LCS) to understand the percolation process. Percolation curves demonstrate that the non-Gaussianity in the HI field increases as reionization progresses. The large clusters in both the HI overdense and underdense excursion sets possess similar values of "thickness" ($T$), as well as "breadth" ($B$), but their third Shapefinder - "length" ($L$) - becomes almost proportional to their volume. The large clusters in both HI overdense and underdense segments are overwhelmingly filamentary. The 'cross-section' of a filamentary cluster can be estimated using the product of the first two Shapefinders, $T \times B$. Hence the cross sections of the large clusters at the onset of percolation do not vary much with volume and their sizes only differ in terms of their lengths. This feature appears more vividly in HI overdense regions than in underdense regions and is more pronounced at lower redshifts which correspond to an advanced stage of reionization.
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