TNG-Cluster模拟中的气体运动图集：从星系团核心到外围
An Atlas of Gas Motions in the TNG-Cluster Simulation: from Cluster Cores to the Outskirts
AI总结：
本文基于TNG-Cluster模拟的352个大质量星系团，系统分析了从核心到外围的气体运动学特征，揭示了核心区流入流出平衡、外围宇宙学吸积主导的双峰分布，以及速度结构函数与暗晕性质和观测的一致性。
摘要：
星系团是研究天体物理过程及其对气体运动学影响的独特实验室。尽管星系团十分重要，但星系团内部及其周围气体运动的全部复杂性仍鲜为人知。本文是介绍新TNG-Cluster模拟首批结果的系列论文之一，该模拟包含352个大质量星系团，涵盖了完整的宇宙学背景、并合、吸积、重子过程、反馈和磁场。通过研究气体流的动力学和相干性，我们发现星系团核心和中间区域的气体运动在很大程度上处于流入和流出之间的平衡状态，呈现出以零速度为中心的高斯分布。在外围区域，即使净速度分布也变得不对称，呈现出双峰特征，其中第二个峰反映了宇宙学吸积。在所有星系团区域中，由此得到的净流分布揭示了复杂的气体动力学。这些特征与暗晕性质密切相关：在给定的星系团总质量下，非弛豫、形成较晚、黑洞质量较小且吸积率较低的暗晕表现出更强的动力学行为。我们的分析表明，视线方向气体速度与径向气体速度之间没有明确关系，这意味着仅凭视线方向速度不足以区分流入和流出气体。温度等其他性质有助于打破这种简并。速度结构函数（VSF）分析表明，外围区域的气体运动更为相干，而朝向暗晕中心的运动学则更加受扰动。在所有星系团区域中，VSF的斜率都接近Kolmogorov理论模型（1/3），但在星系团核心50 kpc范围内除外，那里的斜率明显更陡。TNG-Cluster的结果与对星系团中多相气体在不同尺度上的VSF观测结果广泛一致，尺度范围从1 kpc到兆秒差距。
英文摘要：
Galaxy clusters are unique laboratories for studying astrophysical processes and their impact on gas kinematics. Despite their importance, the full complexity of gas motion within and around clusters remains poorly known. This paper is part of a series presenting first results from the new TNG-Cluster simulation, a suite of 352 massive clusters including the full cosmological context, mergers, accretion, baryonic processes, feedback, and magnetic fields. Studying the dynamics and coherence of gas flows, we find that gas motions in cluster cores and intermediate regions are largely balanced between inflows and outflows, exhibiting a Gaussian distribution centered at zero velocity. In the outskirts, even the net velocity distribution becomes asymmetric, featuring a double peak where the second peak reflects cosmic accretion. Across all cluster regions, the resulting net flow distribution reveals complex gas dynamics. These are strongly correlated with halo properties: at a given total cluster mass, unrelaxed, late-forming halos with less massive black holes and lower accretion rates exhibit a more dynamic behavior. Our analysis shows no clear relationship between line-of-sight and radial gas velocities, suggesting that line-of-sight velocity alone is insufficient to distinguish between inflowing and outflowing gas. Additional properties, such as temperature, can help break this degeneracy. A velocity structure function (VSF) analysis indicates more coherent gas motion in the outskirts and more disturbed kinematics towards halo centers. In all cluster regions, the VSF shows a slope close to the theoretical models of Kolmogorov (1/3), except within 50 kpc of the cluster cores, where the slope is significantly steeper. The outcome of TNG-Cluster broadly aligns with observations of the VSF of multiphase gas across different scales in galaxy clusters, ranging from 1 kpc to Megaparsec scales.
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