EVOLUTION OF SHOCKS AND TURBULENCE IN MAJOR CLUSTER MERGERS
EVOLUTION OF SHOCKS AND TURBULENCE IN MAJOR CLUSTER MERGERS
复制标题
大型集群合并中冲击和动荡的演变
DOI：
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发表时间：
2010
期刊：
影响因子：
--
通讯作者：
K. Mannheim
中科院分区：
文献类型：
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作者：
S. Paul;L. Iapichino;F. Miniati;J. Bagchi;K. Mannheim
我们进行了一组宇宙学模拟的星系团的主要合并，以研究合并冲击的演化和随后的注入湍流的冲击后的区域和在集群内的介质（ICM）。计算已经进行了网格为基础的，自适应网格细化流体动力学代码恩佐，使用的细化标准，特别是设计用于细化湍流附近的冲击。当一个主要的合并事件发生时，大量的湍流能量被注入新形成的集群的ICM。我们的模拟表明，在一个主要的合并后发射的冲击发展成椭球形，并通过与合并集群周围的非线性宇宙网的相互作用而被打破。沿激波传播方向的激波后区域沿着的大小约为300 kpc h-1，该区域的湍流速度弥散大于100 km s-1。我们进行了缩放分析的湍流能量在我们的集群样本。湍流能量与团簇质量的标度关系符合M5/3，这也是自相似团簇模型中热能的标度律。这清楚地表明在团簇演化过程中，粒子化与湍流注入之间存在着密切的联系。至于在集群核心的湍流，我们发现，在2 Gyr后的主要合并（ICM中的冲击传播的时间尺度），湍流的总压力的比例大于10%，约4 Gyr后，它仍然大于5%，一个典型的值为近松弛的集群。因此，星系团中心的湍流持续了几个千兆年，这比湍流再加速模型中通常假设的要长得多，用来解释观测到的射电晕的统计数据。最后讨论了我们的模拟与合并星团A3376外围发现的“对称射电遗迹”在形态学和其他物理参数上的惊人相似性。特别是，合并激波和围绕集群的细丝之间的相互作用可以解释双遗迹边缘的“凹口状”特征的存在。
We performed a set of cosmological simulations of major mergers in galaxy clusters, in order to study the evolution of merger shocks and the subsequent injection of turbulence in the post-shock region and in the intra-cluster medium (ICM). The computations have been performed with the grid-based, adaptive mesh refinement hydrodynamical code Enzo, using a refinement criterion especially designed for refining turbulent flows in the vicinity of shocks. When a major merger event occurs, a substantial amount of turbulence energy is injected in the ICM of the newly formed cluster. Our simulations show that the shock launched after a major merger develops an ellipsoidal shape and gets broken by the interaction with the filamentary cosmic web around the merging cluster. The size of the post-shock region along the direction of shock propagation is of the order of 300 kpc h−1, and the turbulent velocity dispersion in this region is larger than 100 km s-1. We performed a scaling analysis of the turbulence energy within our cluster sample. The best fit for the scaling of the turbulence energy with the cluster mass is consistent with M5/3, which is also the scaling law for the thermal energy in the self-similar cluster model. This clearly indicates the close relation between virialization and injection of turbulence in the cluster evolution. As for the turbulence in the cluster core, we found that within 2 Gyr after the major merger (the timescale for the shock propagation in the ICM), the ratio of the turbulent to total pressure is larger than 10%, and after about 4 Gyr it is still larger than 5%, a typical value for nearly relaxed clusters. Turbulence at the cluster center is thus sustained for several gigayears, which is substantially longer than typically assumed in the turbulent re-acceleration models, invoked to explain the statistics of observed radio halos. Striking similarities in the morphology and other physical parameters between our simulations and the “symmetrical radio relics” found at the periphery of the merging cluster A3376 are finally discussed. In particular, the interaction between the merger shock and the filaments surrounding the cluster could explain the presence of “notch-like” features at the edges of the double relics.
DOI：
10.1086/591228
发表时间：
2008-06
期刊：
The Astrophysical Journal
影响因子：
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作者：
E. Scannapieco;M. Brüggen
通讯作者：
E. Scannapieco;M. Brüggen