Hydrodynamic Simulations of a Moving Substructure in a Cluster of Galaxies: Cold Fronts and Turbulence Generation
Hydrodynamic Simulations of a Moving Substructure in a Cluster of Galaxies: Cold Fronts and Turbulence Generation
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DOI：
10.1086/431927
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发表时间：
2005-05
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影响因子：
--
通讯作者：
M. Takizawa
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文献类型：
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作者：
M. Takizawa
我们进行三维流体动力学模拟星系团中的移动子结构。我们研究了在较大星系团引力势中径向移动的子结构内部和周围的团内介质（ICM）的动力学演化及其观测结果。亚结构通过大团簇中心后，在其前方形成一个弓形激波和明显的接触间断，在模拟合成的X射线图像上，接触间断看起来像一个尖锐的冷锋。这与1 E 0657-56中发现的结构一致。流动结构在第一次转向之前保持层流，因为冲压压力剥离在子结构和周围ICM之间的边界上的Kelvin-Helmholtz不稳定性的发展上占主导地位。当一个子团围绕较大的团的中心径向振荡时，Kelvin-Helmholtz和Rayleigh-Taylor不稳定性发展良好，并且流动结构变得高度湍流。在转弯处，子星系团的冷气体被推出其势阱。因此，冷气体成分似乎在子星系团的前面。一个相对钝的冷锋出现在模拟的X射线图像中，因为接触不连续性被瑞利-泰勒不稳定性扰动。这可以解释在A168中发现的ICM结构。
We perform three-dimensional hydrodynamic simulations of a moving substructure in a cluster of galaxies. We investigate dynamical evolution of the intracluster medium (ICM) in and around the substructure moving radially in the larger cluster's gravitational potential, and its observational consequences. After the substructure passes the larger cluster's center, a bow shock and clear contact discontinuity form in front of it. The contact discontinuity looks like a sharp cold front in the X-ray image synthesized from the simulation results. This agrees with a structure found in 1E 0657-56. The flow structure remains laminar before the first turnaround because the ram pressure stripping is dominant over the development of Kelvin-Helmholtz instabilities on the boundary between the substructure and the ambient ICM. When a subcluster oscillates radially around the larger cluster's center, both Kelvin-Helmholtz and Rayleigh-Taylor instabilities develop well and the flow structure becomes highly turbulent. Around the turnaround, the subcluster's cold gas is pushed out of its potential well. Therefore, the cold gas component appears to be in front of the subcluster. A relatively blunt cold front appears in the simulated X-ray image because the contact discontinuity is perturbed by Rayleigh-Taylor instabilities. This can explain the ICM structure found in A168.