发表机构
Duke University; California Institute of Technology; Max-Planck-Institut für Astronomie; University of Maryland, Baltimore County (UMBC); NASA/Goddard Space Flight Center（杜克大学; 加州理工学院; 马克斯·普朗克天文学研究所; 马里兰大学巴尔的摩分校; 美国宇航局戈达德太空飞行中心）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究利用XMM-牛顿与钱德拉X射线观测对比MACS J1752.0+4440和ZwCl 1856.8+6616两个双射电 relic 星系团并合体，结合TNG-Cluster模拟揭示二者不同动力学状态及相似构型的差异。
AI 中文摘要
利用深度 XMM-牛顿与钱德拉观测，我们对拥有双射电 relic 的星系团并合体 MACS J1752.0+4440 和 ZwCl 1856.8+6616 进行了对比研究。二者均为质量比 1:1 的并合系统，射电 relic 的间距相近，但总质量相差近一个数量级。在 MACS J1752.0+4440 中，东北侧 relic 处的面亮度不连续给出马赫数 $M_{\rho}=1.4\pm0.2$，而温度跃变提供的约束更弱，$2\sigma$ 水平下对应 $M_{kT}\lesssim2.3$，低于射电推导的 $M_{\rm radio}=3.1\pm0.1$；西南侧 relic 处未检测到不连续。热力学图与轴向剖面显示，在百万秒差距尺度的剥离气体结构中存在幸存的低熵核心；X 射线尾的亮度近均匀，且与第三个引力透镜质量峰重合的西南平台，支持非零碰撞参数与复杂并合历史。在 ZwCl 1856.8+6616 中，两个 relic 处均未检测到清晰的面亮度不连续；北侧 X 射线峰领先其最亮团星系（BCG）和引力透镜峰，而温度更高的南侧 X 射线峰则与其 BCG 和引力透镜峰横向偏移，不对称的团内发射支持系统处于近第一次远心点或之后的阶段，此时位移气体可形成类似弹弓的形态。我们给出两个 TNG-Cluster 模拟的类似系统：小质量并合后发生一次离轴大质量碰撞，产生类似 MACS J1752.0+4440 的延展 X 射线尾，后续形成类似 ZwCl 1856.8+6616 的气体结构。X 射线形态独立证实了基于射电 relic 计时推断的并合阶段，即 MACS J1752.0+4440 处于第一次远心点之前，而 ZwCl 1856.8+6616 处于第一次远心点之后，证明相似的射电 relic 与引力透镜构型可对应不同的动力学状态。
英文摘要
Using deep XMM-Newton and Chandra observations, we compare the double-radio-relic galaxy cluster mergers MACS J1752.0+4440 and ZwCl 1856.8+6616. Both are 1:1 mass-ratio mergers with similar relic separations but differing nearly an order of magnitude in total mass. In MACS J1752.0+4440, the surface-brightness discontinuity at the northeastern relic yields Mach $M_ρ=1.4\pm0.2$, while the temperature jump provides a weaker constraint, corresponding to $M_{kT}\lesssim2.3$ at the $2σ$ level, lower than the radio-derived $M_{\rm radio}=3.1\pm0.1$. No discontinuity is detected at the southwestern relic. Thermodynamic maps and axial profiles reveal surviving relatively low-entropy cores embedded in Mpc-scale stripped-gas structures. The nearly uniform X-ray tail brightness and a southwestern plateau coincident with a third lensing mass peak favor a non-zero impact parameter and complex assembly history. In ZwCl 1856.8+6616, we do not detect a clear surface brightness discontinuity at either relic. The northern X-ray peak leads its brightest cluster galaxy (BCG) and lensing peak, while the hotter southern X-ray peak is laterally offset from its BCG and lensing peak. The asymmetric intracluster emission favors a phase near or after first apocenter, when displaced gas can develop a slingshot-like morphology. We present two TNG-Cluster analogs in which a minor merger followed by an off-axis major collision produces extended X-ray tails resembling MACS J1752.0+4440 and later leads to gas structures resembling ZwCl 1856.8+6616. X-ray morphology independently confirms the merger phases inferred from relic-based chronometry, placing MACS J1752.0+4440 before and ZwCl 1856.8+6616 after first apocenter, and demonstrating that similar relic and lensing configurations can correspond to distinct dynamical states.
Comments27 pages, 14 figures, submitted to ApJ
