星系团中速度各向异性组装偏置的观测证据
Observational Evidence of Velocity Anisotropy Assembly Bias in Galaxy Clusters
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中文总结 AI 辅助
利用eROSITA和DESI巡天的91个星系团，通过Jeans动力学建模测量速度各向异性，首次观测证实了速度各向异性组装偏置：各向同性星系团成团性更强。
中文摘要 AI 辅助
宇宙学模拟表明，暗物质晕的成团性不仅取决于质量，还依赖于其次级内部属性，这一效应被称为组装偏置。特别地，数值模型已显示，内部速度各向异性（$\beta$）是与次级晕偏置联系最紧密的晕属性：在固定质量下，具有各向同性速度分布的晕成团性更强，而径向运动占主导的晕成团性较弱。尽管这一理论预测十分稳健，但速度各向异性组装偏置的直接观测探测一直难以实现。本文利用eROSITA和DESI巡天中的大质量星系团样本，提供了该效应的观测证据。我们通过MAMPOSSt进行Jeans动力学建模，测量了91个星系团的内部轨道各向异性$\beta$，并考虑了三种各向异性剖面模型以确保结果的稳健性。我们将样本分为两个子群体：各向同性和径向各向异性，并验证了它们在晕质量上没有显著差异。为了量化它们的大尺度成团性，我们测量了投影互相关函数。我们报告了速度各向异性组装偏置的证据：内部运动学各向同性的星系团比径向主导的星系团表现出更强的成团性，这种分离不太可能归因于星系团质量的残余差异。这一趋势在三种各向异性剖面下显著性有所不同，从轻微倾向到高度显著的信号。此外，当将样本限制为在三种模型中均被一致分类的星系团时，组装偏置仍然清晰存在。
英文摘要
Cosmological simulations show that halo clustering depends on secondary internal properties beyond mass, an effect known as assembly bias. In particular, numerical models have shown that internal velocity anisotropy ($β$) is the halo property most tightly linked to secondary halo bias: at fixed mass, haloes with isotropic velocity profiles are more strongly clustered, whereas haloes in which radial motions dominate are more weakly clustered. Despite this robust theoretical prediction, direct observational detection of velocity anisotropy assembly bias has remained elusive. Here we present observational evidence for this effect using a sample of massive galaxy clusters from the eROSITA and DESI surveys. We measure the internal orbital anisotropy $β$ for 91 clusters via Jeans dynamical modelling with MAMPOSSt, considering three anisotropy profile models to ensure robustness. We divided the sample into two subpopulations: isotropic and radially anisotropic, verifying that they show no significant differences in halo mass. To quantify their large-scale clustering, we measured the projected cross-correlation function with We report evidence of velocity anisotropy assembly bias: clusters with isotropic internal kinematics exhibit stronger clustering than radially dominated ones, a segregation that is unlikely to be attributable to residual differences in cluster mass. This trend shows varying significance across three anisotropy profiles, from a mild tendency to a highly pronounced signal. Furthermore, the assembly bias remains distinct when restricting the sample to clusters consistently classified across all three models.
发表机构
- CONICET. Instituto de Astronomía Teórica y Experimental (IATE)（阿根廷国家科学研究委员会理论与实验天体物理研究所）
- Universidad Nacional de Córdoba (UNC). Observatorio Astronómico de Córdoba (OAC)（科尔多瓦国立大学科尔多瓦天文台）
- INAF-Osservatorio Astronomico di Trieste（意大利国家天体物理研究所的里雅斯特天文台）
- IFPU Institute for Fundamental Physics of the Universe（宇宙基础物理研究所）
- Centre for Particle Cosmology, University of Pennsylvania（宾夕法尼亚大学粒子宇宙学中心）
- Departamento de Física, Universidad Técnica Federico Santa María（智利费德里科·Santa María理工大学物理系）
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