2dFGRS超结构对于分层模型是一个问题吗？
Are the 2dFGRS superstructures a problem for hierarchical models?
摘要：
我们引入了一个客观的方法来评估发现极端事件的概率分布的冷暗物质，如空洞，超密度或非常高的质量晕。我们的方法使用一个N体模拟的层次聚类的暗物质，以找到极端的结构。极端事件的频率，在我们的例子中，细胞或平滑体积与最高计数的集群质量暗物质晕，是很好地描述了一个Gumbel分布。然后，这种分布可以用来预测发现更多极端事件的概率，否则需要更大的模拟集合来量化。我们使用我们的技术来评估发现大质量星系团或超星系团集中的机会，就像在两度视场星系红移巡天（2dFGRS）中发现的两个，使用细胞计数分析。Gumbel分布给出了一个很好的描述极端细胞计数的分布在两个大的合奏模拟涵盖不同的宇宙学，也当测量在实空间和红移空间的集群。我们在模拟中发现了类似于2dFGRS中发现的结构的例子。在等于2dFGRS的体积中发现这种结构的机会约为2%。
英文摘要：
We introduce an objective method to assess the probability of finding extreme events in the distribution of cold dark matter such as voids, overdensities or very high mass haloes. Our approach uses an ensemble of N-body simulations of the hierar- chical clustering of dark matter to find extreme structures. The frequency of extreme events, in our case the cell or smoothing volume with the highest count of cluster-mass dark matter haloes, is well described by a Gumbel distribution. This distribution can then be used to forecast the probability of finding even more extreme events, which would otherwise require a much larger ensemble of simulations to quantify. We use our technique to assess the chance of finding concentrations of massive clusters or super- clusters, like the two found in the two-degree field galaxy redshift survey (2dFGRS), using a counts-in-cells analysis. The Gumbel distribution gives an excellent descrip- tion of the distribution of extreme cell counts across two large ensembles of simulations covering different cosmologies, and also when measuring the clustering in both real and redshift space. We find examples of structures like those found in the 2dFGRS in the simulations. The chance of finding such structures in a volume equal to that of the 2dFGRS is around 2%.
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