Comparing the temperatures of galaxy clusters from hydrodynamical N-body simulations to Chandra and XMM-Newton observations
Comparing the temperatures of galaxy clusters from hydrodynamical N-body simulations to Chandra and XMM-Newton observations
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DOI：
10.1111/j.1365-2966.2004.08167.x
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发表时间：
2004-04
影响因子：
4.8
通讯作者：
P. Mazzotta;E. Rasia;L. Moscardini;G. Tormen;Department of Physics University of RomeTor Vergata-Department-of-Physics-University-of-RomeTor-Vergata-1389703112;Italy Harvard-Smithsonian Center for Astrophysics;U. D. D. Astronomia-U.-D.-D.-Astronomia-1411788185;U. Padova;I. D. D. Astronomia-I.-D.-D.-Astronomia-102389674;U. Bologna;It
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文献类型：
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作者：
P. Mazzotta;E. Rasia;L. Moscardini;G. Tormen;Department of Physics University of RomeTor Vergata-Department-of-Physics-University-of-RomeTor-Vergata-1389703112;Italy Harvard-Smithsonian Center for Astrophysics;U. D. D. Astronomia-U.-D.-D.-Astronomia-1411788185;U. Padova;I. D. D. Astronomia-I.-D.-D.-Astronomia-102389674;U. Bologna;It
在X射线区域，对指导星系和星系团形成和演化的物理过程的理论研究主要是基于数值流体动力学N体模拟的结果，而这些结果又往往直接与X射线观测结果进行比较。虽然原则上微不足道，但这些比较并不总是简单的。我们证明了从X射线观测得到的热复杂团簇的投影光谱温度总是低于在数值模拟分析中广泛使用的发射加权温度。我们表明，这种温度偏差主要是有关的事实，即发射加权温度不反映实际的光谱特性的观测源。这对研究星系团的热结构具有重要意义，特别是当存在强温度梯度时，如激波阵面。由于这种偏差，在真实的观测中，激波锋面看起来比辐射加权温度图预测的要弱得多，甚至可能检测不到。这也许可以解释为什么，尽管数值模拟预测激波锋面是星系团中相当常见的特征，但迄今为止，很少有观测对象能清楚地看到它们。为了解决这个问题，我们提出了一个新的公式，光谱般的温度函数，并表明，对于高于3千电子伏的温度，它近似的光谱温度，以更好的百分之几，使模拟更直接地与观察。
Theoretical studies of the physical processes guiding the formation and evolution of galaxies and galaxy clusters in the X-ray region are mainly based on the results of numerical hydrodynamical N-body simulations, which in turn are often directly compared with X-ray observations. Although trivial in principle, these comparisons are not always simple. We demonstrate that the projected spectroscopic temperature of thermally complex clusters obtained from X-ray observations is always lower than the emission-weighed temperature, which is widely used in the analysis of numerical simulations. We show that this temperature bias is mainly related to the fact that the emission-weighted temperature does not reflect the actual spectral properties of the observed source. This has important implications for the study of thermal structures in clusters, especially when strong temperature gradients, such as shock fronts, are present. Because of this bias, in real observations shock fronts appear much weaker than what is predicted by emission-weighted temperature maps, and may not even be detected. This may explain why, although numerical simulations predict that shock fronts are a quite common feature in clusters of galaxies, to date there are very few observations of objects in which they are clearly seen. To fix this problem we propose a new formula, the spectroscopic-like temperature function, and show that, for temperatures higher than 3 keV, it approximates the spectroscopic temperature to better than a few per cent, making simulations more directly comparable to observations.