COSMOS X-ray Group Catalog

COSMOS is an astronomical survey designed to probe the formation and evolution of galaxies as a function of cosmic time (redshift) and large scale structural environment. The survey covers a 2 square degree equatorial field with imaging by most of the major space-based telescopes (Hubble, Spitzer, GALEX, XMM, Chandra) and a number of large ground based telescopes (Subaru, VLA, ESO-VLT, UKIRT, NOAO, CFHT, and others). Over 2 million galaxies are detected, spanning 75% of the age of the universe. This is a COSMOS X-ray group membership catalog, combining X-ray group properties from Finoguenov et al. (2007) with estimates for masses and radii calibrated from weak lensing (Leauthaud et al. 2010), and member galaxy information (George et al. 2011). Group redshifts have been determined by searching for red sequence overdensities within 500 kpc of the X-ray centers and are refined by using spectroscopic redshifts when available. We use groups with z<1 to ensure good optical identifications and small photoz uncertainties. This dataset or service is made available by the Infrared Science Archive (IRSA) at IPAC, which is operated by the California Institute of Technology under contract with the National Aeronautics and Space Administration.

COSMOS巡天是一项旨在探究星系形成与演化随宇宙时间（红移(redshift)）及大尺度结构环境变化规律的天文观测项目。该巡天覆盖2平方度的赤道天区，使用了绝大多数主流空间望远镜（哈勃(Hubble)、斯皮策(Spitzer)、GALEX、XMM、钱德拉(Chandra)）与多台大型地面望远镜（昴星团望远镜(Subaru)、甚大阵(VLA)、欧洲南方天文台甚大望远镜(ESO-VLT)、英国红外望远镜(UKIRT)、美国国家光学天文台(NOAO)、加拿大-法国-夏威夷望远镜(CFHT)等）开展成像观测。此次巡天共探测到超过200万个星系，观测覆盖了宇宙年龄的75%。本数据集为COSMOS X射线星系团成员表，整合了Finoguenov等人（2007）提出的X射线星系团属性、基于弱引力透镜(weak lensing)校准得到的质量与半径估算值（Leauthaud等人，2010），以及星系团成员星系信息（George等人，2011）。星系团的红移通过在X射线中心500千秒差距(kpc)范围内搜寻红序(red sequence)过密区确定，并在有可用光谱红移时通过光谱红移进行修正优化。我们选取红移z<1的星系团，以保障良好的光学证认效果与较小的光度量红移(photometric redshift，简称photoz)不确定性。本数据集或服务由加州理工学院(California Institute of Technology)按与美国国家航空航天局(National Aeronautics and Space Administration，简称NASA)的合同委托运营的IPAC下属红外科学档案馆(Infrared Science Archive, IRSA)对外提供。