Clusters of Galaxies: Insights into Large-Scale Structure Formation and Galaxy Evolution

当今天文学中的两个基本问题是星系分布中的结构是如何形成的，以及环境在多大程度上影响星系的演化。对附近五个星系团正在进行的调查得出了令人惊讶的结果(Zabludoff等人。1995年)强调了观测星系团的力量，以获得数据来理解这些问题。这项研究将包括对三个独特的、精心挑选的星系团和较小星系群的样本的观察。观测结果将被用来，1)对星系团的形成和宇宙平均质量密度参数欧米茄零施加严格的限制，2)分离星系团环境对星系演化的贡献，3)确定“E+A”星系--那些具有强烈的巴尔默吸收线但没有线发射的奇怪物体--是否是连接蓝色螺旋线和“SO”星系的链中的一环，以及4)揭示暗端星系的形状在星系团中起作用。数据还原和解释的其他结果将包括更好地理解布彻-奥姆勒效应的原因和星系团内介质的演化。这三个样本的观测结果将被用来揭开星系团及其星系的详细演化史。与新一代大型地面望远镜和NASA卫星正在进行的对更高红移系统的类似广泛调查相比，这些结果将为未来的研究提供宝贵的基线。这些项目的结果不仅将给出上述重要问题的答案，而且也将是规划对附近星系团及其星系进行最广泛调查的第一步，也是必要的一步。Warrick Couch(安格洛-澳大利亚天文台和澳大利亚国立大学)、Ian Smail(卡内基天文台)和Ann Zabludoff(卡内基天文台)计划使用英澳望远镜(AAT)的2DF多光纤光谱仪及其400根光纤，在一个定义良好、体积有限的样本中观测大约50个丰富星系团中的10,000-20,000个星系。2DF项目在未来五年内完成的时间与其他主要的星系红移调查(拉斯坎帕纳斯、斯隆数字天空调查和AAT红移调查)的完成情况相匹配。为了了解所有类型的星系是如何演化的，需要像这样的大型统计调查，对组成环境进行抽样。2DF星系团调查将对密集环境分布的远尾进行采样，这些区域强烈依赖于早期宇宙的条件，因此是对宇宙学模型的有力测试。2DF项目的时机也将与有望对大规模结构形成(Evrard、Steinmetz、Lake等)进行新的N体/流体动力学模拟的时间重合，具有足够的动态范围，以包括每个宇宙中的数十个星团，同时保持足够的分辨率来监测单个星系的演化。这将是第一次，可以将星系团动力学和星系团星系演化的细节与理论宇宙学模型的预测直接进行比较。***

Zabludoff - Abstract Two of the fundamental questions in astronomy today are how structures form in the galaxy distribution and to what extent environment affects galaxy evolution. Surprising results from an on-going survey of five nearby galaxy clusters (Zabludoff et al. 1995) underscore the power of observing clusters of galaxies for data to understand these issues. The research will consist of observations of three unique, carefully chosen samples of clusters of galaxies and smaller groups of galaxies. The results from the observations will be used to, 1) to place stringent constraints on how clusters of galaxies form and on the cosmological mean mass density parameter Omega zero, 2) to isolate the contribution of the cluster environment to galaxy evolution, 3) to determine whether "E+A" galaxies, those strange objects with strong Balmer absorption lines but no line emission, are a link in the chain that connects blue spirals to "SO" galaxies, and 4) to uncover the shape of the faint-end galaxy luminosity function in clusters. Additional results from the reduction and interpretation of the data will include a better understanding of the causes of the Butcher-Oemler effect and of the evolution of the intracluster medium. The results of the observations of the three samples will be used to unravel the detailed evolutionary history of clusters and their galaxies. The results will provide invaluable baselines for future research, when compared with similarly extensive surveys of higher redshift systems underway with the new generation of large ground-based telescopes and NASA satellites . The results from the projects will not only yield answers to the important questions discussed above, but will also be the first and necessary step in the planning of the most extensive survey of nearby clusters and their galaxies ever conceived. Warrick Couch (Ang lo-Australian Observatory and Australia National University), Ian Smail (Carnegie Observatories), and Ann Zabludoff (Carnegie Observatories) are planning to use the Anglo- Australian Telescope's (AAT) 2DF multi-fiber spectrograph, with its 400 fibers, to observe 10,000-20,000 galaxies in approximately 50 rich clusters in a well defined, volume-limited sample. The completion of the 2DF project in the next five years is timed to match the completion of other major redshift surveys of galaxies (Las Campanas, Sloan Digital Sky Survey, and AAT redshift surveys). To understand how all types of galaxies evolve, large statistical surveys like these, which sample comple mentary environments, are needed. The 2DF cluster survey will sample the far tail of the distribution of dense environments, regions which are strongly dependent on the conditions in the early universe and are thus powerful tests of cosmological models. The timing of the 2DF project will also coincide with promising new N-body/hydrodynamic simulations of large-scale structure formation (Evrard, Steinmetz, Lake, and others), with enough dynamic range to include tens of clusters per universe, while maintaining sufficient resolution to monitor the evolution of individual galaxies. For the first time, it will be possible to compare the details of cluster dynamics and cluster galaxy evolution directly with the predictions of theoretical cosmological models. ***