High Redshift Optically-Selected Galaxy Clusters

大约红移1的星系团为研究从单个星系到最大的宇宙结构的演化提供了一个独特的机会。然而，目前在这些高红移的星团样本仍然很小。这项工作涉及红星团序列（RCS）调查，这是一项新的光学星团调查，旨在发现高红移的星团，同时最大限度地减少许多困扰早期星团光学调查的污染源。光谱和光学/近红外成像活动代表了对RCS样品的第一次详细的后续观测。主要目标是确认星团红移，评估成功率，并校准星团丰富度的光度估计。对第一个子样本的观察将校准整个RCS调查，该调查预计在z 0.8处包含200个群集。对星团蓝色部分、星团内人口梯度和星团星系恒星形成历史的进一步详细测量将追踪恒星形成场星系进入星团的过程，以及它们最终转变为红色、被动演化的星团人口。使用哈勃太空望远镜、钱德拉、XMM和BIMA的相关程序将提供有关星团质量、星团内部介质和星系形态的额外信息。结合先前对低红移星团的研究结果，该项目将详细追踪宇宙年龄的很大一部分星团的演化

AST-0206154Ellingson, EricaGalaxy clusters at redshift approximately one offer a unique opportunity to study evolution, ranging from individual galaxies to the largest cosmic structures. However, current samples of clusters at these high redshifts are still small. This work involves the Red Cluster Sequence (RCS) Survey, a new optical cluster survey which has been designed to discover clusters at high redshift while minimizing many of the contamination sources that have plagued earlier optical surveys for clusters. The spectroscopic and optical/near-infrared imaging campaign represents the first detailed follow-up observations of the RCS sample. The primary goal is to confirm the cluster redshifts, evaluate success rates, and calibrate photometric estimates of cluster richness. Observations of this first subsample will calibrate the entire RCS survey, which is expected to contain 200 clusters at z 0.8. Further detailed measurements of cluster blue fractions, population gradients within clusters and the star formation histories of cluster galaxies will trace the infall of star forming field galaxies into clusters, and their eventual transformation into a red, passively-evolving cluster populations. Related programs using the Hubble Space Telescope, Chandra, XMM, and BIMA will provide additional information on cluster masses, the intra-cluster medium and galaxy morphologies. Together with previous results for lower redshift clusters, this program will trace in detail the evolution of clusters over a large fraction of the age of the universe.***