活动星系核驱动的星系团中Turbulence的亚网格模拟
Subgrid Modeling of AGN-Driven Turbulence in Galaxy Clusters
摘要：
由活动星系核（AGN）提供动力的热而密度不足的气泡可能在阻止冷核星系团中心的灾难性冷却方面发挥关键作用。我们提出了三维模拟，捕捉这种气泡的演变，使用自适应网格流体动力学代码，FLASH 3，我们已经添加了一个亚网格模型的湍流和混合。虽然纯水模拟表明，AGN气泡被打乱到分辨率依赖的口袋中的密度不足的气体，适当的亚网格湍流建模表明，这是一个很差的近似湍流级联，继续远远超出分辨率限制。相反，瑞利-泰勒不稳定性有效地将加热区域与其周围环境混合，同时将其保留为相干结构，与观测结果一致。因此，当气泡在流体静力学的团内介质（ICM）中向外移动时，它们就变成了混合物质的热云，就像大型空中爆炸在地球的流体静力学大气中上升时会导致独特的“蘑菇云”结构一样。正确地捕捉这些云的演变对许多ICM属性具有重要意义。特别是，它显着改变了活动星系核对熵和金属在冷核集群，如英仙座的分布的影响。
英文摘要：
Hot, underdense bubbles powered by active galactic nuclei (AGN) are likely to play a key role in halting catastrophic cooling in the centers of cool-core galaxy clusters. We present three-dimensional simulations that capture the evolution of such bubbles, using an adaptive-mesh hydrodynamic code, FLASH3, to which we have added a subgrid model of turbulence and mixing. While pure-hydro simulations indicate that AGN bubbles are disrupted into resolution-dependent pockets of underdense gas, proper modeling of subgrid turbulence indicates that this a poor approximation to a turbulent cascade that continues far beyond the resolution limit. Instead, Rayleigh-Taylor instabilities act to effectively mix the heated region with its surroundings, while at the same time preserving it as a coherent structure, consistent with observations. Thus bubbles are transformed into hot clouds of mixed material as they move outwards in the hydrostatic intracluster medium (ICM), much as large airbursts lead to a distinctive ``mushroom cloud'' structure as they rise in the hydrostatic atmosphere of Earth. Properly capturing the evolution of such clouds has important implications for many ICM properties. In particular, it significantly changes the impact of AGN on the distribution of entropy and metals in cool-core clusters such as Perseus.
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