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arXiv 2408.03083astro-ph.COastro-ph.GA
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宇宙网中纤维状结构的统计特性

Statistical properties of filaments in the cosmic web

Youcai Zhang, Hong Guo, Xiaohu Yang, Peng Wang

备注：
12 pages, 11 figures. Accepted for publication in MNRAS
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AI总结：

本研究基于ELUCID模拟，利用Hessian矩阵分类与COWS中轴算法，分析宇宙网纤维结构的统计特性，明确了平滑长度、阈值参数对纤维长度分布与径向密度剖面的影响规律。

摘要：

在宇宙学及约束ELUCID模拟（数值模拟项目）的框架下，本研究探究了宇宙网中纤维状结构的统计特征，重点关注纤维长度分布、径向密度剖面等方面。研究借助密度场的Hessian矩阵（海森矩阵）完成宇宙网环境分类，核心分析宇宙结构对$R_{\rm s}$（平滑长度）与$λ_{\rm th}$（阈值参数）两个变量的响应规律。结果显示，节点、纤维、薄片、空洞的体积占比受阈值参数$λ_{\rm th}$的影响极强，仅受平滑长度$R_{\rm s}$的轻微影响。研究采用COWS方法的中轴细化算法确定圆柱状纤维的中心轴，观测发现纤维长度中位数随平滑长度增大呈上升趋势；对不同$R_{\rm s}$取值下的纤维长度函数分析表明，随$R_{\rm s}$增大，短纤维数量减少、长纤维数量增加，长度分布在约$2.5R_{\rm s}$处达到峰值。此外，纤维的径向密度剖面受$R_{\rm s}$与$λ_{\rm th}$参数的影响显著，在约$2R_{\rm s}$处存在一个谷值，阈值升高会使密度剖面的振幅增大；同时，短纤维的密度剖面通常比长纤维的密度更高。

英文摘要：

In the context of the cosmological and constrained ELUCID simulation, this study explores the statistical characteristics of filaments within the cosmic web, focussing on aspects such as the distribution of filament lengths and their radial density profiles. Using the classification of the cosmic web environment through the Hessian matrix of the density field, our primary focus is on how cosmic structures react to the two variables $R_{\rm s}$ and $λ_{\rm th}$. The findings show that the volume fractions of knots, filaments, sheets, and voids are highly influenced by the threshold parameter $λ_{\rm th}$, with only a slight influence from the smoothing length $R_{\rm s}$. The central axis of the cylindrical filament is pinpointed using the medial-axis thinning algorithm of the COWS method. It is observed that median filament lengths tend to increase as the smoothing lengths increase. Analysis of filament length functions at different values of $R_{\rm s}$ indicates a reduction in shorter filaments and an increase in longer filaments as $R_{\rm s}$ increases, peaking around $2.5R_{\rm s}$. The study also shows that the radial density profiles of filaments are markedly affected by the parameters $R_{\rm s}$ and $λ_{\rm th}$, showing a valley at approximately $2R_{\rm s}$, with increases in the threshold leading to higher amplitudes of the density profile. Moreover, shorter filaments tend to have denser profiles than their longer counterparts.

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