邻近冷核星系团Hydra A和A478的中心质量分布
Central Mass Profiles of the Nearby Cool-core Galaxy Clusters Hydra A and A478
摘要：
我们对附近的冷核星系团Hydra A（$z=0.0538$）和A478（$z=0.0881$）进行了弱透镜研究，其中最亮的星系团（BCGs）拥有强大的活动星系核（AGN）活动。对于每个集群，所观察到的切向剪切剖面是很好地描述了一个单一的Navarro-弗伦克-怀特模型或两个组件的模型，包括BCG作为一个未解决的质点。对于A478，我们确定的BCG和它的主机晕质量从联合适合弱透镜和恒星测光测量。我们发现，初始质量函数（IMF）的选择可以引入一个因素的两个不确定性的BCG质量，而BCG主机晕质量是很好的数据约束。我们进行了联合分析的弱透镜和恒星运动学数据可用于长蛇座A集群，这使我们能够约束的中央质量分布，而无需假设特定的IMF。我们发现，从联合分析确定的中心质量分布（$r<300$ kpc）是在良好的协议与独立的测量，包括动力学质量估计从冷气盘组件，X射线流体静力学总质量估计，和中心恒星质量估计的基础上Salpeter IMF。观察到的暗物质馏分周围的BCG水螅A被发现是小于绝热收缩模型预测的，这表明其他物理过程的重要性，如活动星系核的反馈和/或耗散合并。
英文摘要：
We perform a weak-lensing study of the nearby cool-core galaxy clusters, Hydra A ($z=0.0538$) and A478 ($z=0.0881$), of which brightest cluster galaxies (BCGs) host powerful activities of active galactic nuclei (AGNs). For each cluster, the observed tangential shear profile is well described either by a single Navarro--Frenk--White model or a two-component model including the BCG as an unresolved point mass. For A478, we determine the BCG and its host-halo masses from a joint fit to weak-lensing and stellar photometry measurements. We find that the choice of initial mass functions (IMFs) can introduce a factor of two uncertainty in the BCG mass, whereas the BCG host halo mass is well constrained by data. We perform a joint analysis of weak-lensing and stellar kinematics data available for the Hydra A cluster, which allows us to constrain the central mass profile without assuming specific IMFs. We find that the central mass profile ($r<300$kpc) determined from the joint analysis is in excellent agreement with those from independent measurements, including dynamical masses estimated from the cold gas disk component, X-ray hydrostatic total mass estimates, and the central stellar mass estimated based on the Salpeter IMF. The observed dark-matter fraction around the BCG for Hydra A is found to be smaller than those predicted by adiabatic contraction models, suggesting the importance of other physical processes, such as the the AGN feedback and/or dissipationless mergers.
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