The eROSITA Final Equatorial-Depth Survey (eFEDS): Optical confirmation, redshifts, and properties of the cluster and group catalog
The eROSITA Final Equatorial-Depth Survey (eFEDS): Optical confirmation, redshifts, and properties of the cluster and group catalog
复制标题
eROSITA 最终赤道深度巡天 (eFEDS)：光学确认、红移以及星团和星团目录的属性
DOI：
10.1051/0004-6361/202141123
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发表时间：
2021
影响因子：
6.5
通讯作者：
Driver S. P.
中科院分区：
文献类型：
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作者：
Klein M.;Oguri M.;Mohr J. J.;Grandis S.;Ghirardini V.;Liu T.;Liu A.;Bulbul E.;Wolf J.;Comparat J.;Ramos-Ceja M. E.;Buchner J.;Chiu I.;Clerc N.;Merloni A.;Miyatake H.;Miyazaki S.;Okabe N.;Ota N.;Pacaud F.;Salvato M.;Driver S. P.
背景2019年，俄罗斯-德国频谱伦琴伽马（SRG）卫星上的eROSITA望远镜开始进行深度全天X射线巡天，目标是在四年内识别约10万个星团和星团。作为其性能验证阶段的一部分，进行了约 140 度的勘测，称为 eROSITA 最终赤道深度勘测 (eFEDS)。凭借四年后全天巡天的典型深度，它可以测试工具和方法，并改进全天巡天的预测。目标作为这项工作的一部分，编制了 542 个 X 射线选定的星系群和星团候选目录。在本文中，我们提出了光学跟踪，旨在为整个样本提供红移和簇确认。此外，我们的目标是提供有关星团的动态状态、丰富度和光学中心的附加信息。最后，我们的目标是评估光学簇确认对 X 射线选定样本的纯度和完整性的影响。方法我们使用来自 Hyper Suprime-Cam Subaru 战略计划和遗产调查的光学成像数据来识别 X 射线检测到的候选簇的光学对应物。我们利用多组件匹配滤光片簇确认工具 (MCMF) 以及光学簇探测器 CAMIRA 来导出簇红移和丰富度。 MCMF 提供了光学结构与 X 射线候选物偶然叠加的概率。这些概率用于识别最佳光学对应物以及确认 X 射线候选物作为簇。使用光学到 X 射线缩放关系以及模拟来估计此确认过程对目录纯度和完整性的影响。生成的目录还与公共组和集群目录相匹配。基于星团红移处红色序列星系的密度图构建了星团动态光学估计器。结果通过为所有 542 个候选者提供红移估计，我们构建了 477 个星团和群的光学确认样本，残留污染率为 6%。其中，470个（98.5%）是使用MCMF确认的，并且通过与光谱组目录交叉匹配添加了7个系统。使用可观察到可观察的缩放和应用的确认阈值，我们预测 8 ± 2 个真实系统已被排除在构建此低污染样本所需的 MCMF 削减之外。这个数字与通过交叉匹配发现但未得到 MCMF 确认的 7 个系统非常吻合。该目录的预测红移和质量分布与模拟非常吻合。因此，我们预计这 477 个系统包含候选列表中所有真实集群的 99% 以上。使用独立于 MCMF 的方法，我们确认已确认子样本的目录污染率为 6 ± 3%。对完整候选列表应用相同的方法可得到 17 ± 3%，这与来自约 17% 的已确认系统比例的估计以及约 20% 的模拟预期一致。我们还提供了基于簇动态状态的导出估计量的合并簇候选样本。
ContextIn 2019, the eROSITA telescope on board the Russian-German satellite Spectrum-Roentgen-Gamma (SRG) began to perform a deep all-sky X-ray survey with the aim of identifying ~100 000 clusters and groups over the course of four years. As part of its performance verification phase, a ~140 deg2survey, called eROSITA Final Equatorial-Depth Survey (eFEDS), was performed. With a depth typical of the all-sky survey after four years, it allows tests of tools and methods as well as improved predictions for the all-sky survey.AimsAs part of this effort, a catalog of 542 X-ray selected galaxy group and cluster candidates was compiled. In this paper we present the optical follow-up, with the aim of providing redshifts and cluster confirmation for the full sample. Furthermore, we aim to provide additional information on the dynamical state, richness, and optical center of the clusters. Finally, we aim to evaluate the impact of optical cluster confirmation on the purity and completeness of the X-ray selected sample.MethodsWe used optical imaging data from the Hyper Suprime-Cam Subaru Strategic Program and from the Legacy Survey to identify optical counterparts to the X-ray detected cluster candidates. We make use of the multi-component matched filter cluster confirmation tool (MCMF), as well as of the optical cluster finder CAMIRA to derive cluster redshifts and richnesses. MCMF provided the probabilities with which an optical structure would be a chance superposition with the X-ray candidate. These probabilities were used to identify the best optical counterpart as well as to confirm an X-ray candidate as a cluster. The impact of this confirmation process on catalog purity and completeness was estimated using optical to X-ray scaling relations as well as simulations. The resulting catalog was furthermore matched with public group and cluster catalogs. Optical estimators of the cluster dynamical state were constructed based on density maps of the red-sequence galaxies at the cluster redshift.ResultsBy providing redshift estimates for all 542 candidates, we construct an optically confirmed sample of 477 clusters and groups with a residual contamination of 6%. Of these, 470 (98.5%) are confirmed using MCMF, and 7 systems are added through cross-matching with spectroscopic group catalogs. Using observable-to-observable scaling and the applied confirmation threshold, we predict that 8 ± 2 real systems have been excluded with the MCMF cut required to build this low-contamination sample. This number agrees well with the 7 systems found through cross-matching that were not confirmed with MCMF. The predicted redshift and mass distribution of this catalog agree well with simulations. Thus, we expect that these 477 systems include >99% of all true clusters in the candidate list. Using an MCMF-independent method, we confirm that the catalog contamination of the confirmed subsample is 6 ± 3%. Application of the same method to the full candidate list yields 17 ± 3%, consistent with estimates coming from the fraction of confirmed systems of ~17% and with expectations from simulations of ~20%. We also present a sample of merging cluster candidates based on the derived estimators of the cluster dynamical state.