X射线选择MACS与光学选择星系团的RCS透镜效应
The lensing efficiencies of MACS X-ray selected versus RCS optically selected galaxy clusters
摘要：
星系团样本中强透镜弧的统计数据提供了有关星系团结构的信息，这些信息与单个星系团的信息是互补的。然而，迄今为止已经分析过的星团样本要么很小，要么不均匀，要么观察到的角分辨率有限。我们测量的透镜弧统计97集群成像高角分辨率与哈勃太空望远镜，识别透镜弧使用两个自动弧检测算法。该样品包括类似数量的X射线选择（MACS）和光学选择（RCS）集群，并跨越集群红移范围为0.2 < z < 1。我们在所选的X射线子样本中编制了42个弧和在光学子样本中编制了7个弧的星表。除五条弧线外，所有这些弧线都是首次报道。在0.3 < z < 0.7时，X射线选择的簇具有显著更高的弧的平均频率，每个簇1.2+/-0.2，而光学样品中为0.2+/-0.1。尽管X射线团簇和光学团簇具有相似的光学光度，但显著不同的透镜效应表明，X射线团簇追踪的质量浓度要大得多。质量差也由X射线团的较低空间密度和光学样品中少数弧的小爱因斯坦半径支持。更高层次的影响，如浓度或子结构的差异，也可能有所贡献。
英文摘要：
The statistics of strongly lensed arcs in samples of galaxy clusters provide information on cluster structure that is complementary to that from individual clusters. However, samples of clusters that have been analyzed to date have been either small, heterogeneous, or observed with limited angular resolution. We measure the lensed-arc statistics of 97 clusters imaged at high angular resolution with the Hubble Space Telescope, identifying lensed arcs using two automated arc detection algorithms. The sample includes similar numbers of X-ray selected (MACS) and optically selected (RCS) clusters, and spans cluster redshifts in the range 0.2 < z < 1. We compile a catalogue of 42 arcs in the X-ray selected subsample and 7 arcs in the optical subsample. All but five of these arcs are reported here for the first time. At 0.3 < z < 0.7, the X-ray selected clusters have a significantly higher mean frequency of arcs, 1.2+/-0.2 per cluster, versus 0.2+/-0.1 in the optical sample. The strikingly different lensing efficiencies indicate that X-ray clusters trace much larger mass concentrations, despite the similar optical luminosities of the X-ray and optical clusters. The mass difference is supported also by the lower space density of the X-ray clusters, and by the small Einstein radii of the few arcs in the optical sample. Higher-order effects, such as differences in concentration or substructure, may also contribute.
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