发表机构
Nara Women’s University; Argelander-Institut für Astronomie (AIfA), Universität Bonn; Yale University（奈良女子大学; 波恩大学阿尔兰德天体物理研究所; 耶鲁大学）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究对比XRISM观测与TNG-Cluster模拟，发现方位角变化和投影效应可部分解释非热压力占比不足，但Abell 2029的极低值仍需罕见动力学条件或缺失物理过程说明。
AI 中文摘要
星系团内介质（ICM）的气体运动可探测星系团的形成、反馈及非热压力支撑，但近期XRISM观测显示，速度弥散度与非热压力占比系统性低于模拟预测，极端系统如Abell 2029的数值低于几乎所有模拟星系团。利用TNG-Cluster模拟，我们发现非热压力占比对冷核状态和形成历史敏感，并提供了一个双尺度拟合函数，可捕捉径向分布的内部冷核抑制与外部上升特征。通过正向建模模拟XRISM观测并将其与投影及本征三维量对比，我们发现方位角变化与投影效应是观测到的速度弥散度及非热压力占比不足的原因，该偏差随半径增大，部分抵消了真实三维非热压力占比的本征向外上升趋势。然而，这些效应无法解释Abell 2029观测到的极低非热压力占比，在仅湍流及湍流加整体运动两种定义下，其在每个测量半径处均低于模拟冷核星系团分布的约0-6百分位。剩余张力表明，当前ICM模型中存在罕见动力学条件或缺失物理过程影响气体运动幅度。
英文摘要
Intracluster medium (ICM) gas motions probe cluster assembly, feedback, and non-thermal pressure support, but recent XRISM observations reveal velocity dispersions and non-thermal pressure fractions systematically lower than simulations predict, with extreme systems such as Abell 2029 falling below nearly all simulated clusters. Using the TNG-Cluster simulations, we show that the non-thermal pressure fraction depends sensitively on cool-core state and formation history, and provide a two-scale fitting function capturing both the inner cool-core suppression and outer rise of the radial profile. By forward-modeling mock XRISM observations and comparing them with both projected and intrinsic three-dimensional quantities, we find that azimuthal variations and projection effects contribute to the deficit in the observed velocity dispersion and non-thermal pressure fraction. This bias increases with radius and partially offsets the intrinsic outward rise in the true three-dimensional non-thermal pressure fraction. However, these effects cannot explain the extremely low values of the non-thermal pressure fraction observed in Abell 2029, which fall below approximately the 0th-6th percentiles of the simulated cool-core cluster distribution at every measured radius under both the turbulence-only and turbulence-plus-bulk definitions. The remaining tension points to rare dynamical conditions or missing physics affecting the amplitude of gas motions in current ICM models.
Comments17 pages, 12 Figures. Matching the accepted PASJ version
