一个视线星系团碰撞的模拟X射线观测
A Line-Of-Sight Galaxy Cluster Collision: Simulated X-Ray Observations
摘要：
几条证据表明，星系团Cl~0024+17，一个表面上松弛的系统，实际上是两个星系团的碰撞，相互作用发生在我们的视线上。在本文中，我们提出了一个高分辨率的$N$体/流体动力学模拟这样的碰撞。我们已经创建了模拟X射线观测我们的模拟系统使用MARX，一个程序，模拟钱德拉X射线天文台的在轨性能。我们分析这些模拟数据，以产生径向轮廓的表面亮度和温度。在稍后的时间，$t = 2.0-3.0$ Gyr碰撞后，模拟的表面亮度轮廓更好地拟合由两个$β$模型轮廓的叠加比一个单一的轮廓，在协议的观测Cl~0024+17。一般来说，由于投影效应，星系团碰撞后的密度和温度结构在观测中是看不到的。特别是，从光谱拟合观察到的温度远低于最热气体的温度。我们确定从我们的拟合的配置文件，如果系统被建模为一个单一的集群，流体静力学的质量估计是一个因素$\sim$ 2-3小于实际质量，但如果系统被建模为两个星系团叠加，流体静力学的质量估计可以作出这是准确的$\sim$ 10%。我们研究了这些结果对星系团X射线巡天的影响。
英文摘要：
Several lines of evidence have suggested that the 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. In this paper we present a high-resolution $N$-body/hydrodynamics simulation of such a collision. We have created mock X-ray observations of our simulated system using MARX, a program that simulates the on-orbit performance of the Chandra X-ray Observatory. We analyze these simulated data to generate radial profiles of the surface brightness and temperature. At later times, $t = 2.0-3.0$ Gyr after the collision, the simulated surface brightness profiles are better fit by a superposition of two $β$-model profiles than a single profile, in agreement with the observations of Cl~0024+17. In general, due to projection effects, much of the post-collision density and temperature structure of the clusters is not seen in the observations. In particular, the observed temperatures from spectral fitting are much lower than the temperature of the hottest gas. We determine from our fitted profiles that if the system is modeled as a single cluster, the hydrostatic mass estimate is a factor $\sim$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 $\sim$10%. We examine some implications of these results for galaxy cluster X-ray surveys.
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