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Simulations of binary galaxy cluster mergers: Modeling real clusters and exploring parameter spaces.

机译：二元星系星团合并的模拟：对真实星团建模并探索参数空间。

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摘要

We present an investigation of controlled N-body/hydrodynamics high-resolution simulations of binary galaxy cluster mergers, performed using the FLASH code. In addition to analyzing the quantities directly from the simulation, we produce simulated X-ray observations of the cluster ICM and perform standard analyses of the surface brightness distribution and spectra of the X-ray photons emitted from the hot cluster gas. Several lines of evidence have suggested that the galaxy cluster Cl 0024+17, an apparently relaxed system, is actually a collision of two clusters, the interaction occurring along our line of sight. We present a high-resolution N-body/hydrodynamics simulation of such a collision. We analyze mock X-ray observations of our simulated clusters to generate radial profiles of the surface brightness and temperature to show that at later times the simulated surface brightness profiles are better fit by a superposition of two beta-model profiles than a single profile, in agreement with the observations of Cl 0024+17. We determine from our fitted profiles that if the system is modeled as a single cluster, the hydrostatic mass estimate is a factor ∼2-3 less than the actual mass, but if the system is modeled as two galaxy clusters in superposition, a hydrostatic mass estimation can be made which is accurate to within ∼10%. Additionally, recent lensing observations of Cl 0024+17 suggest the presence of a ring-like dark matter structure, which has been interpreted as the result of such a collision. To determine the conditions under which such a feature would form, we vary the initial velocity anisotropy of the dark matter particles. Our simulations show a ring feature does not occur even when the initial particle velocity distribution is highly tangentially anisotropic. Only when the initial particle velocity distribution is circular do our simulations show such a feature, which is consistent with the halo velocity distributions seen in cosmological simulations. Lastly, we present a fiducial set of galaxy cluster merger simulations, where the initial mass ratio and the impact parameter have been varied. By projecting the simulated quantities along the axes of the computational domain, we produce maps of X-ray surface brightness, temperature, projected mass density, and simulated X-ray observations. From these observations we compute the observed X-ray luminosity and fitted spectral temperature, and fit beta-model profiles to compute estimated hydrostatic masses. From this information we determine the effect of mergers viewed along different projections on these observed quantities. We also construct simulated maps of galaxies, and test the power of a commonly employed substructure statistic to probe for the existence of substructure along the different projections during the merger. Finally, we comment on other aspects of our simulations, such as comparisons to existing merging clusters; and the mixing of the intracluster medium due to merging, and resulting cluster entropy and cooling time profiles.
机译：我们目前对使用FLASH代码执行的二元星系团合并的受控N体/流体动力学高分辨率模拟进行研究。除了直接从模拟中分析量之外，我们还对团簇ICM进行了模拟X射线观察，并对从热团簇气体发出的X射线光子的表面亮度分布和光谱进行了标准分析。有几条证据表明，星系团Cl 0024 + 17是一个看似放松的系统，实际上是两个星团的碰撞，相互作用是沿着我们的视线发生的。我们提出了这种碰撞的高分辨率N体/流体动力学模拟。我们分析了模拟簇的模拟X射线观察结果，以生成表面亮度和温度的径向分布图，表明在以后的时间中，通过叠加两个beta模型分布图比单个分布图更好地拟合了模拟表面亮度分布图。与Cl 0024 + 17的观察结果一致。我们根据拟合的轮廓确定，如果将系统建模为单个星团，则静水质量估计比实际质量小约2-3倍，但是如果将系统建模为两个星系星团重叠，则为静水质量可以做出准确的估计，准确度在〜10％以内。另外，最近对Cl 0024 + 17的透镜观察表明存在环状暗物质结构，这被解释为这种碰撞的结果。为了确定形成这种特征的条件，我们改变了暗物质粒子的初始速度各向异性。我们的模拟显示，即使初始粒子速度分布具有高度切向各向异性，也不会出现环形特征。只有当初始粒子速度分布为圆形时，我们的模拟才会显示出这种特征，这与宇宙模拟中看到的光晕速度分布是一致的。最后，我们介绍了一个星系团合并模拟的基准集，其中初始质量比和影响参数已发生变化。通过沿着计算域的轴投影模拟量，我们可以生成X射线表面亮度，温度，投影质量密度和模拟X射线观测图。从这些观察值中，我们可以计算出观察到的X射线光度和拟合的光谱温度，并拟合beta模型轮廓以计算估计的静水质量。根据这些信息，我们可以确定对这些观察到的数量进行不同预测的合并所产生的影响。我们还构建了星系的模拟图，并测试了常用子结构统计量的功能，以探测合并过程中沿着不同投影的子结构的存在。最后，我们对仿真的其他方面进行评论，例如与现有合并集群的比较；以及由于合并而导致的集群内介质的混合以及由此产生的集群熵和冷却时间分布。

著录项

  • 作者

    ZuHone, John A.;

  • 作者单位

    The University of Chicago.;

  • 授予单位 The University of Chicago.;
  • 学科 Physics Astronomy and Astrophysics.;Computer Science.
  • 学位 Ph.D.
  • 年度 2009
  • 页码 149 p.
  • 总页数 149
  • 原文格式 PDF
  • 正文语种 eng
  • 中图分类 天文学;自动化技术、计算机技术;
  • 关键词

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