The Merger Dynamics of the Galaxy Cluster A1775: New Insights from Chandra and XMM-Newton for a Cluster Simultaneously Hosting a Wide-angle Tail and a Narrow-angle Tail Radio Source
The Merger Dynamics of the Galaxy Cluster A1775: New Insights from Chandra and XMM-Newton for a Cluster Simultaneously Hosting a Wide-angle Tail and a Narrow-angle Tail Radio Source
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DOI：
10.3847/1538-4357/abf09e
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发表时间：
2021-03
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通讯作者：
D. Hu;Haiguang Xu;Zhenghao Zhu;C. Shan;Yongkai Zhu;Shida Fan;Yuanyuan Zhao;Chengze Liu;Hoongwah Siew;Zhongli Zhang;L. Gu;M. Johnston-Hollitt;X. Kang;Q. Tan;Jiang Chang;Xiang-Ping Wu
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作者：
D. Hu;Haiguang Xu;Zhenghao Zhu;C. Shan;Yongkai Zhu;Shida Fan;Yuanyuan Zhao;Chengze Liu;Hoongwah Siew;Zhongli Zhang;L. Gu;M. Johnston-Hollitt;X. Kang;Q. Tan;Jiang Chang;Xiang-Ping Wu
通过分析高质量的Chandra和XMM-Newton档案数据，我们提出了一个新的研究A1775的合并动力学。我们确认/识别弧形边缘（即，在X射线峰值以西约48 kpc处有一个分裂的冷气尾部，向东延伸到约163 kpc，还有一个螺旋状的X射线过剩羽流（在星团核心东北约81-324 kpc范围内）连接到尾部的末端。的头部，通过该投影气体温度上升向外从千电子伏，被发现是一个冷锋与马赫数。沿冷锋和尾翼表面的沿着分布，可观察到典型的Kelvin-Helmholtz不稳定性特征（机头和机翼等）。并将其用于约束磁场上限（Δ 11.2 μG）和粘度抑制因子（Δ 0.01）。结合光学和射电证据，我们提出了一个两体合并（而不是在一个大尺度的气体环境中的系统运动）的情况下，并进行了理想化的流体动力学模拟来验证它，我们发现，所观察到的X射线辐射和温度分布可以最好地再现合并质量比为5后的第一个近心通道。因此NAT射电星系更有可能是一个以2800 km s−1的相对速度落入星团中心的单个星系，这个速度受到其射电形态的限制。下落的子星系团预计有一个相对较低的气体含量，因为只有一个气体贫乏的子星系团才能引起这样一个离轴合并中观察到的只有中心的扰动。
We present a new study of the merger dynamics of A1775 by analyzing the high-quality Chandra and XMM-Newton archival data. We confirm/identify an arc-shaped edge (i.e., the head) at ∼48 kpc west of the X-ray peak, a split cold gas tail that extends eastward to ∼163 kpc, and a plume of spiral-like X-ray excess (within about 81–324 kpc northeast of the cluster core) that connects to the end of the tail. The head, across which the projected gas temperature rises outward from to keV, is found to be a cold front with a Mach number of . Along the surfaces of the cold front and tail, typical Kelvin–Helmholtz instability features (noses and wings, etc.) are found and are used to constrain the upper limit of the magnetic field (∼11.2 μG) and the viscosity suppression factor (∼0.01). Combining optical and radio evidence, we propose a two-body merger (instead of systematic motion in a large-scale gas environment) scenario and have carried out idealized hydrodynamic simulations to verify it. We find that the observed X-ray emission and temperature distributions can be best reproduced with a merger mass ratio of 5 after the first pericentric passage. The NAT radio galaxy is thus more likely to be a single galaxy falling into the cluster center at a relative velocity of 2800 km s−1, a speed constrained by its radio morphology. The infalling subcluster is expected to have a relatively low gas content, because only a gas-poor subcluster can cause central-only disturbances as observed in such an off-axis merger.