Z>1时最大质量团簇SPT-CL J2106-5844的精确质量测定
Precise Mass Determination of SPT-CL J2106-5844, the Most Massive Cluster at z>1
摘要：
我们对SPT-CL J2106-5844在z=1.132处进行了详细的高分辨率弱透镜（WL）研究，据称这是在南极望远镜Sunyaev-Zel'dovich（SPT-SZ）调查中发现的z > 1的最大质量系统。基于哈勃空间望远镜上的高级巡天照相机和宽视场照相机3的深度成像数据，我们发现星团质量分布是不对称的，由一个主星团和一个位于其以西约640 kpc的子星团组成。中央团块进一步分解为两个较小的西北和东南子结构，相隔约150 kpc。我们发现，这个相当复杂的质量分布是更一致的集群星系分布比以前提出的单峰分布。西北部的亚结构与BCG峰和X射线峰一致，而东南部的亚结构与数密度峰的位置一致。这些形态特征以及与X射线辐射的比较表明，该星系团可能是一个合并系统。我们估计该星系团的维里质量为$M_{200c} = (10.4^{+3.3}_{-3.0}\pm1.0)~\times~10^{14}~M_{\odot}$，其中第二个误差条是系统的不确定性。我们的结果证实了星系团SPT-CL J2106-5844确实是迄今为止已知的z>1的最大质量星系团。我们通过对质心、质量浓度关系和样本方差进行不同假设的测试来证明这种质量估计的稳健性。
英文摘要：
We present a detailed high-resolution weak-lensing (WL) study of SPT-CL J2106-5844 at z=1.132, claimed to be the most massive system discovered at z > 1 in the South Pole Telescope Sunyaev-Zel'dovich (SPT-SZ) survey. Based on the deep imaging data from the Advanced Camera for Surveys and Wide Field Camera 3 on-board the Hubble Space Telescope, we find that the cluster mass distribution is asymmetric, composed of a main clump and a subclump ~640 kpc west thereof. The central clump is further resolved into two smaller northwestern and southeastern substructures separated by ~150 kpc. We show that this rather complex mass distribution is more consistent with the cluster galaxy distribution than a unimodal distribution as previously presented. The northwestern substructure coincides with the BCG and X-ray peak while the southeastern one agrees with the location of the number density peak. These morphological features and the comparison with the X-ray emission suggest that the cluster might be a merging system. We estimate the virial mass of the cluster to be $M_{200c} = (10.4^{+3.3}_{-3.0}\pm1.0)~\times~10^{14}~M_{\odot}$, where the second error bar is the systematic uncertainty. Our result confirms that the cluster SPT-CL J2106-5844 is indeed the most massive cluster at z>1 known to date. We demonstrate the robustness of this mass estimate by performing a number of tests with different assumptions on the centroids, mass-concentration relations, and sample variance.
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