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arXiv 1107.5740astro-ph.CO
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星系团合并引起的散射和偏差-- Sunyaev-Zeldovich效应标度关系

Merger induced scatter and bias in the cluster mass - Sunyaev-Zeldovich effect scaling relation

Elisabeth Krause, Elena Pierpaoli, Klaus Dolag, Stefano Borgani

摘要:

利用从宇宙学流体动力学模拟中提取的星系团样本,研究了星系团质量与热Sunyaev-Zeldovich(SZ)效应之间标度关系的散射源。总的来说,质量-SZ比例关系的分散与质量-晕浓度关系中的分散很好地相关,其中更集中的晕在固定质量下具有更强的集成SZ信号。内在散射的其他来源是相关结构的投影效应,这导致散射分布偏离对数正态分布,并使其向更高的推断质量和集群的动力学状态倾斜。我们在高时间分辨率下模拟了39个星系团及其宇宙学环境,研究了合并星系团的演化。这个样本使我们能够研究的第一次详细的合并集群周围的尺度关系的合并参数的宇宙学代表性分布的演变。主要合并造成不对称的分散,合并系统的推断质量偏低。我们发现合并是偏向低推断质量的主要来源:超过50%的标度关系的这一边的离群值在过去的千兆年内经历了一次重大合并。由于动态扰动集群的比例随红移的增加,我们的分析表明,合并导致红移依赖的偏差的标度关系。此外,我们发现大规模集群的SZ形态与集群的动力学状态有很好的相关性,这表明形态可以用来约束合并分数和识别合并引起的标度关系的异常值。

英文摘要:

We examine sources of scatter in scaling relations between galaxy cluster mass and thermal Sunyaev-Zeldovich (SZ) effect using cluster samples extracted from cosmological hydrodynamical simulations. Overall, the scatter of the mass-SZ scaling relation is well correlated with the scatter in the mass-halo concentration relation with more concentrated halos having stronger integrated SZ signals at fixed mass. Additional sources of intrinsic scatter are projection effects from correlated structures, which cause the distribution of scatter to deviate from log-normality and skew it towards higher inferred masses, and the dynamical state of clusters. We study the evolution of merging clusters based on simulations of 39 clusters and their cosmological environment with high time resolution. This sample enables us to study for the first time the detailed evolution of merging clusters around the scaling relation for a cosmologically representative distribution of merger parameters. Major mergers cause an asymmetric scatter such that the inferred mass of merging systems is biased low. We find mergers to be the dominant source of bias towards low inferred masses: over 50% of outliers on this side of the scaling relation underwent a major merger within the last Gigayear. As the fraction of dynamically disturbed clusters increases with redshift, our analysis indicates that mergers cause a redshift-dependent bias in scaling relations. Furthermore, we find the SZ morphology of massive clusters to be well correlated with the clusters' dynamical state, suggesting that morphology may be used to constrain merger fractions and identify merger-induced outliers of the scaling relation.

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