The Physics of Cluster Mergers
The Physics of Cluster Mergers
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DOI：
10.1007/0-306-48096-4_1
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发表时间：
2001-05
期刊：
影响因子：
--
通讯作者：
C. Sarazin
中科院分区：
文献类型：
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作者：
C. Sarazin
星系团通常是由较小的星系团和星系团的引力合并形成的。主要星团合并是宇宙大爆炸以来最活跃的事件。将讨论合并的一些基本物理特性，重点是简单的分析论证而不是数值模拟。回顾了合并率的半解析估计，并给出了二元合并运动学的简单处理。合并将激波驱动到簇内介质中，这些激波加热了气体，并且还加速了非热相对论粒子。冲击的 X 射线观察可用于确定合并的几何形状和运动学。许多集群包含冷却流核心；讨论了合并过程中这些核心与较热、密度较小的气体的流体动力学相互作用。由于激波中粒子加速，星系团应该包含非常大量的相对论电子和离子。洛伦兹因子γ∼300（能量E=γmec2∼150 MeV）的电子预计将特别常见。描述了在这些合并中加速的非热粒子的无线电、极紫外线、硬 X 射线和伽马射线发射的观测和模型。
Clusters of galaxies generally form by the gravitational merger of smaller clusters and groups. Major cluster mergers are the most energetic events in the Universe since the Big Bang. Some of the basic physical properties of mergers will be discussed, with an emphasis on simple analytic arguments rather than numerical simulations. Semi-analytic estimates of merger rates are reviewed, and a simple treatment of the kinematics of binary mergers is given. Mergers drive shocks into the intracluster medium, and these shocks heat the gas and should also accelerate nonthermal relativistic particles. X-ray observations of shocks can be used to determine the geometry and kinematics of the merger. Many clusters contain cooling flow cores; the hydrodynamical interactions of these cores with the hotter, less dense gas during mergers are discussed. As a result of particle acceleration in shocks, clusters of galaxies should contain very large populations of relativistic electrons and ions. Electrons with Lorentz factorsγ∼300 (energiesE=γmec2∼150 MeV)are expected to be particularly common. Observations and models for the radio, extreme ultraviolet, hard X-ray, and gamma-ray emission from nonthermal particles accelerated in these mergers are described.