ESO远星系团巡天（EDisCS）中星系团的光谱学。II。最近15个场中星系团的红移、速度色散和亚结构
Spectroscopy of clusters in the ESO distant cluster survey (EDisCS).II. Redshifts, velocity dispersions, and substructure for clusters in the last 15 fields
摘要：
目标。作为ESO远星系团巡天（EDisCS）的一部分，我们在15个巡天中对星系进行了光谱观测。我们确定的红移和速度分散的星系团位于这些领域，我们测试可能的子结构的集群。方法.我们在VLT使用FORS 2仪器获得了多目标掩模光谱。我们减少了数据，特别注意天空减法。我们实现了Kelson的方法，用于在对数据进行任何重组/插值之前执行天空减法。从测量的星系红移，我们确定集群的速度分散体使用bifweight估计和测试可能的子结构中使用的Dressler-Shectman测试的集群。结果在数据的任何重新分箱/内插之前减去天空的方法提供光子噪声有限的结果，而在数据已经被重新分箱/内插之后减去天空的传统方法导致来自倾斜狭缝的光谱的显著更大的噪声。给出了单个星系的红移和21个星系团的红移和速度色散。对于至少有20个光谱确认的成员的9个集群，我们提出了从Dressler-Shectman检验获得的子结构的存在的统计显著性，并在两个集群中检测到子结构。结论.加上我们以前的论文中的数据，光谱和光谱速度色散现在可用于26个EDisCS星系团，其红移范围为0.40-0.96，速度色散范围为166-1080 km/s。
英文摘要：
AIMS. We present spectroscopic observations of galaxies in 15 survey fields as part of the ESO Distant Cluster Survey (EDisCS). We determine the redshifts and velocity dispersions of the galaxy clusters located in these fields, and we test for possible substructure in the clusters. METHODS. We obtained multi-object mask spectroscopy using the FORS2 instrument at the VLT. We reduced the data with particular attention to the sky subtraction. We implemented the method of Kelson for performing sky subtraction prior to any rebinning/interpolation of the data. From the measured galaxy redshifts, we determine cluster velocity dispersions using the biweight estimator and test for possible substructure in the clusters using the Dressler-Shectman test. RESULTS. The method of subtracting the sky prior to any rebinning/interpolation of the data delivers photon-noise-limited results, whereas the traditional method of subtracting the sky after the data have been rebinned/interpolated results in substantially larger noise for spectra from tilted slits. Redshifts for individual galaxies are presented and redshifts and velocity dispersions are presented for 21 galaxy clusters. For the 9 clusters with at least 20 spectroscopically confirmed members, we present the statistical significance of the presence of substructure obtained from the Dressler-Shectman test, and substructure is detected in two of the clusters. CONCLUSIONS. Together with data from our previous paper, spectroscopy and spectroscopic velocity dispersions are now available for 26 EDisCS clusters with redshifts in the range 0.40-0.96 and velocity dispersions in the range 166-1080 km/s.
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