全脱光了？大质量星系团碰撞MACSJ0553 $-$ 3342中暗物质和亮物质的动力学
Fully stripped? The dynamics of dark and luminous matter in the massive cluster collision MACSJ0553.4$-$3342
摘要：
我们提出了一个非常X射线发光星系团MACSJ 0553.4 -3342（$z = 0.4270$ ;以下简称MACSJ 0553）的多波长调查的结果。结合哈勃太空望远镜和钱德拉X射线天文台获得的高分辨率数据与地面星系光谱学，我们的分析明确地建立了一个大质量星系团的碰撞后合并的二元系统。其主要特征包括发光物质和暗物质完美地排列在一起，形成一个几乎650千秒差距的组成部分（投影）在另一个子星系团的暗物质峰和第二个X射线峰之间，极热的气体（k $T > 15$ keV）在合并轴的两端，在东部的潜在冷锋，一个异常低的气体质量分数约为0.075的西部组件，速度离散度为$1490_{-130}^{+104}$ km s $^{-1}$，沿视线方向没有明显的亚结构迹象。我们认为MACSJ 0553合并不是在天空的平面上进行的，而是在一个大的倾斜角度下进行的，被观察到非常接近转向，并且东部X射线峰是质量稍小的西部分量的冷核，在碰撞过程中被东部子集群完全剥离和捕获。如果这一假设是正确的，那么MACSJ 0553将成为一个极好的目标，可以用来研究冲压压力剥离以及团簇形成过程中亮物质和暗物质的碰撞行为。
英文摘要：
We present the results of a multiwavelength investigation of the very X-ray luminous galaxy cluster MACSJ0553.4-3342 ($z = 0.4270$; hereafter MACSJ0553). Combining high-resolution data obtained with the Hubble Space Telescope and the Chandra X-ray Observatory with ground-based galaxy spectroscopy, our analysis establishes the system unambiguously as a binary, post-collision merger of massive clusters. Key characteristics include perfect alignment of luminous and dark matter for one component, a separation of almost 650 kpc (in projection) between the dark-matter peak of the other subcluster and the second X-ray peak, extremely hot gas (k$T > 15$ keV) at either end of the merger axis, a potential cold front in the east, an unusually low gas mass fraction of approximately 0.075 for the western component, a velocity dispersion of $1490_{-130}^{+104}$ km s$^{-1}$, and no indication of significant substructure along the line of sight. We propose that the MACSJ0553 merger proceeds not in the plane of the sky, but at a large inclination angle, is observed very close to turnaround, and that the eastern X-ray peak is the cool core of the slightly less massive western component that was fully stripped and captured by the eastern subcluster during the collision. If correct, this hypothesis would make MACSJ0553 a superb target for a competitive study of ram-pressure stripping and the collisional behaviour of luminous and dark matter during cluster formation.
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