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Studying the ICM velocity structure within galaxy clusters with simulations and X-ray observations

机译:通过模拟和X射线观察研究星系团中的ICm速度结构

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摘要

Galaxy clusters are optimal laboratories to test cosmology as well as models for physicaludprocesses acting on smaller scales. X–ray observations of the hot gas filling their darkudmatter potential well, i.e. the intra–cluster medium (ICM), still provides one of theudbest ways to investigate the intrinsic properties of clusters. Methods based on X–rayudobservations of the ICM are commonly used to estimate the total mass, assuming thatudthe gas traces the underlying potential well and satisfies spherical symmetry, and thermaludmotions dominate the total pressure support. However, non–thermal motions are likelyudto establish in the ICM, hence, contribute to the total pressure and have to be taken intoudaccount in the mass estimate.udIn this thesis I study the ICM thermo–dynamical structure by combiningudhydrodynamical simulations and synthetic X–ray observations of galaxy clusters. Theudmain goal is to study their gas velocity field and the implications due to non–thermaludmotions: first, by analysing directly the velocity patterns in simulated clusters and,udsecondly, by reconstructing the internal ICM structure from mock X–ray spectra. Toudthis aim, I developed and applied an X–ray photon simulator to obtain synthetic X–rayudspectra from the gas component in hydrodynamical simulations of galaxy clusters.udThe main findings of this work are as follows.ud(i) Ordered, rotational patterns in the gas velocity field in cluster cores can establishudduring the mass assembly process, but are found to be transient phenomena, easilyuddestroyed by passages of gas–rich subhaloes. This suggests that in smoothly growingudhaloes the phenomenon is in general of minor effect. Nonetheless, major mergers orudhighly disturbed systems can indeed develop significant ordered motions and rotation,udwhich contribute up to 20% to the total mass. (ii) It is indeed possible to reconstructudthe thermal structure of the ICM in clusters from X–ray spectral analysis, by recoveringudthe emission measure (EM) distribution of the gas as a function of temperature. This is possible with current X–ray telescopes (e.g. Suzaku) via multi–temperature fitting of X–udray spectra. (iii) High–precision X–ray spectrometers, such as ATHENA, will allow us toudmeasure velocity amplitudes of ICM non–thermal motions, from the velocity broadeningudof heavy–ion (e.g. iron) emission lines. In this work, these achievements are obtained byudapplying the virtual X–ray simulator to generate ATHENA synthetic spectra of simulatedudclusters. The non–thermal velocity of the ICM in the central region is used to furtherudcharacterise the cluster and the level of deviation from the expected self–similarity. Byudexcluding the clusters with the highest non–thermal velocity dispersion, the scatter of theudLX −T relation for the sample is significantly reduced, which will allow for a more preciseudcomparison between observations and simulations.
机译:银河星团是测试宇宙学的最佳实验室,也是作用于较小尺度的物理过程的模型。 X射线观测的热气充满了暗的 udmatter势阱,即群集内介质(ICM),仍然提供了研究簇的内在特性的最佳方法之一。假定气体覆盖了潜在的势阱并满足球对称性,而热运动主导了总压力,则通常使用基于ICM的X射线模拟的方法估算总质量。但是,非热运动很可能会在ICM中建立,因此会影响总压力,因此必须在质量估计中加以考虑。 ud在本文中,我将结合以下内容来研究ICM热力学结构:银河星团的水动力模拟和合成X射线观察。主要目标是研究其气体速度场及其非热运动引起的影响:首先,通过直接分析模拟团簇中的速度模式,其次,通过模拟X射线光谱重建内部ICM结构。为此,我开发并应用了X射线光子模拟器,以从星系团水动力模拟中的气体成分中获得合成X射线 udspec。 ud这项工作的主要发现如下。 ud(i)团簇核心中气体速度场中的有序旋转模式可以在质量组装过程中确立,但被发现是瞬态现象,容易被富气体的次卤代烃通过。这表明在平滑生长的 udhaloes中,该现象通常影响较小。但是,大型合并或受高度干扰的系统确实可以产生明显的有序运动和旋转,这对总质量的贡献高达20%。 (ii)通过恢复气体的排放量(EM)分布作为温度的函数,确实有可能从X射线光谱分析中重建ICM的热结构。当前的X射线望远镜(例如Suzaku)可以通过X- udray光谱的多温度拟合来实现。 (iii)高精度的X射线光谱仪,例如ATHENA,将使我们能够从重离子(例如铁)发射线的速度展宽 ud中测量ICM非热运动的速度振幅。在这项工作中,通过虚拟应用虚拟X射线模拟器生成模拟 udclusters的ATHENA合成光谱可以获得这些成就。 ICM在中心区域的非热速度被用来进一步表征该聚类以及与预期自相似性的偏离水平。通过排除具有最高非热速度色散的聚类,样品的udLX -T关系的散布显着减少,这将使观察与模拟之间的比较精确。

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    Biffi Veronica;

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  • 年度 2012
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