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Resolving galaxy cluster gas properties at z ~ 1 with XMM-Newton and Chandra

机译：用XMM-Newton和Chandra解析z〜1的星系团气体性质

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Massive, high-redshift, galaxy clusters are useful laboratories to test cosmological models and to probe structure formation and evolution, but observations are challenging due to cosmological dimming and angular distance effects. Here we present a pilot X-ray study of the five most massive ( M _(500) & 5 × 10~(14) M _(⊙) ), distant ( z ~ 1 ), clusters detected via the Sunyaev-Zel’Dovich effect. We optimally combine XMM-Newton and Chandra X-ray observations by leveraging the throughput of XMM-Newton to obtain spatially-resolved spectroscopy, and the spatial resolution of Chandra to probe the bright inner parts and to detect embedded point sources. Capitalising on the excellent agreement in flux-related measurements, we present a new method to derive the density profiles, which are constrained in the centre by Chandra and in the outskirts by XMM-Newton . We show that the Chandra - XMM-Newton combination is fundamental for morphological analysis at these redshifts, the Chandra resolution being required to remove point source contamination, and the XMM-Newton sensitivity allowing higher significance detection of faint substructures. Measuring the morphology using images from both instruments, we found that the sample is dominated by dynamically disturbed objects. We use the combined Chandra - XMM-Newton density profiles and spatially-resolved temperature profiles to investigate thermodynamic quantities including entropy and pressure. From comparison of the scaled profiles with the local REXCESS sample, we find no significant departure from standard self-similar evolution, within the dispersion, at any radius, except for the entropy beyond 0.7 R _(500) . The baryon mass fraction tends towards the cosmic value, with a weaker dependence on mass than that observed in the local Universe. We make a comparison with the predictions from numerical simulations. The present pilot study demonstrates the utility and feasibility of spatially-resolved analysis of individual objects at high-redshift through the combination of XMM-Newton and Chandra observations. Observations of a larger sample will allow a fuller statistical analysis to be undertaken, in particular of the intrinsic scatter in the structural and scaling properties of the cluster population.
机译：大规模的高红移星系团是有用的实验室，可用于测试宇宙学模型以及探测结构的形成和演化，但是由于宇宙学变暗和角距离效应，观测工作具有挑战性。在这里，我们介绍了通过Sunyaev-Zel检测到的五个最大质量（M _（500）> 5×10〜（14）M _（⊙）），远距离（z〜1）的星团的X射线试验研究。 '多维奇效应。通过利用XMM-Newton的通量，我们可以最佳地结合XMM-Newton和Chandra X射线观察结果，以获得空间分辨光谱，并通过Chandra的空间分辨率来探测明亮的内部零件和检测嵌入式点源。利用与通量相关的测量中的出色一致性，我们提出了一种导出密度分布的新方法，该分布受Chandra约束在中心，而由XMM-Newton约束在郊区。我们显示，钱德拉-XMM-牛顿组合是这些红移时形态分析的基础，钱德拉分辨率是去除点源污染所必需的，而XMM-牛顿灵敏度则可以检测出较弱的亚结构。使用两种仪器的图像测量形态，我们发现样品受动态干扰对象的控制。我们使用组合的Chandra-XMM-Newton密度分布图和空间分辨的温度分布图来研究热力学量，包括熵和压力。通过将缩放后的轮廓与本地REXCESS样本进行比较，我们发现在任何半径范围内，除了超过0.7 R _（500）的熵之外，均没有明显偏离标准自相似进化。重子质量分数趋于宇宙值，对质量的依赖性比在本地宇宙中观察到的弱。我们与数值模拟的预测结果进行了比较。当前的先导研究通过XMM-Newton和Chandra观测的结合展示了高红移下单个对象的空间分辨分析的实用性和可行性。对较大样本的观察将允许进行更全面的统计分析，尤其是对集群总体的结构和缩放特性的内在分散。

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