标题： 映射中等红移的星团 显示英文标题

标题： Mapping Moderate Redshift Cluster

摘要： 为了检验星系团在大半径处是否具有上升的质光比，并估算10\hmpc尺度上密度波动谱的振幅，加拿大观测宇宙学网络 (CNOC) 星系团合作组正在获取多目标光谱仪速度和双色光度测定数据，这些样本位于高X射线光度星系团的5\hmpc邻域中，其包含$\simeq$1000个星系团星系和$\simeq$2000个场星系，$z\simeq 0.3$。星系团样本的X射线选择基于其势阱深度来筛选天体，并且对投影效应和星系偏差均不敏感。 该星系数据集采用自动光度测定、自动掩模设计、光谱选择模型和精确速度控制选择，将是我们在测试中任何红移下可用的最佳数据集。 测量大半径的质量光比 (M/L) 需要统计地剔除投射到星团红移空间的场星系。 对于中等红移星团，利用大量的前景和背景星系，可以相对准确地完成这一测量。 CNOC 样本还提供了对星团尺度密度波动谱的灵敏测试。 这三十多个每个星团中的红移给出了大约 1000 \kms 的平均速度弥散，这表明$\sigma_8$正规化参数在$0.6\lta \sigma_8\lta 0.9$范围内。 显示英文摘要

摘要： To test whether clusters have rising mass to light ratios at large radii and to estimate the amplitude of the density fluctuation spectrum on the scale of 10\hmpc\ the Canadian Network for Observational Cosmology (CNOC) cluster collaboration is obtaining Multi-Object Spectrograph velocities and two colour photometry for a sample of $\simeq$1000 cluster galaxies and $\simeq$2000 field galaxies in a 5\hmpc\ neighborhood of high X-ray luminosity clusters at $z\simeq 0.3$. X-ray selection of the cluster sample picks out objects on the basis of the depth of their potential well depth, and is insensitive to both projection effects and galaxy biases. The galaxy dataset, with selection controlled using automated photometry, automated mask design, spectral selection modeling, and accurate velocities, will be the best available at any redshift for our tests. Measuring mass-to-light ratios (M/L) at large radii requires a statistical removal of field galaxies projected into the redshift space of the cluster. This can be done relatively accurately for moderate redshift clusters, using the large number of foreground and background galaxies. The CNOC sample also provides a sensitive test of the density fluctuation spectrum on cluster scales. The 30 or so redshifts available in each of three clusters gives an average velocity dispersion of about 1000 \kms which indicates that the $\sigma_8$ normalization parameter is in the range of $0.6\lta \sigma_8\lta 0.9$.