MACSIS模拟中的气体聚集及其对流体静力学偏差的影响
Gas clumping and its effect on hydrostatic bias in the MACSIS simulations
摘要：
我们使用MACSIS流体动力学模拟来估计大质量星系团的团内介质中气体聚集的程度，以及它如何影响流体静力学质量偏差。通过比较成团的方位角散射的排放措施，观测代理，我们发现，它们都随着半径的增加，更大的质量和动态扰动系统。类似的趋势也被视为方位角温度散射和非热压力分数，这两者都与密度波动，这些值也随着红移增加。然而，在最近的工作，我们发现只有一个弱的相关性之间的结块，或其代理人，和流体静力学质量偏差。为了减少投影轮廓中的聚集效应，我们根据最近的观测研究计算方位中值，并发现这减少了偏差中的分散。我们还试图通过使用非热压力项来校正团簇质量，并从3D气体剖面中找到过校正的质量估计值（$1-b=0.86$至$1-b=1.15$），但从投影气体剖面中改进了质量估计值（$1-b=0.75$至$1-b=0.85$），并警告系统性地增加散射。我们的结论是，集群平均质量偏差最小化，从应用非热压力校正（$1-b=0.85$）与更温和的减少，从选择集群，具有低聚块（$1-b=0.79$）或动态放松（$1-b=0.80$）。然而，后一种选择在最小化单个对象的散射方面最有效。这样的结果可以通过配备高分辨率光谱仪（如Athena）的下一代X射线任务进行测试。
英文摘要：
We use the MACSIS hydrodynamical simulations to estimate the extent of gas clumping in the intracluster medium of massive galaxy clusters and how it affects the hydrostatic mass bias. By comparing the clumping to the azimuthal scatter in the emission measure, an observational proxy, we find that they both increase with radius and are larger in higher-mass and dynamically perturbed systems. Similar trends are also seen for the azimuthal temperature scatter and non-thermal pressure fraction, both of which correlate with density fluctuations, with these values also increasing with redshift. However, in agreement with recent work, we find only a weak correlation between the clumping, or its proxies, and the hydrostatic mass bias. To reduce the effect of clumping in the projected profiles, we compute the azimuthal median following recent observational studies, and find this reduces the scatter in the bias. We also attempt to correct the cluster masses by using a non-thermal pressure term and find over-corrected mass estimates ($1-b=0.86$ to $1-b=1.15$) from 3D gas profiles but improved mass estimates ($1-b=0.75$ to $1-b=0.85$) from projected gas profiles, with the caveat of systematically increased scatter. We conclude that the cluster-averaged mass bias is minimised from applying a non-thermal pressure correction ($1-b=0.85$) with more modest reductions from selecting clusters that have low clumping ($1-b=0.79$) or are dynamically relaxed ($1-b=0.80$). However, the latter selection is most effective at minimising the scatter for individual objects. Such results can be tested with next generation X-ray missions equipped with high-resolution spectrometers such as Athena.
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