ARIZONA CLUSTER REDSHIFT SURVEY (ACReS)

星系团是解开星系形成和演化背后的奥秘的关键角色，了解这些奥秘对于揭示我们的宇宙如何演化以及了解我们自己的银河系如何开始是必要的。 星系团长期以来一直被认为是星系演化的活跃场所，尽管驱动这些转变的物理过程尚未建立。 最近的研究表明，即使在离星系团中心很远的地方，星系群看起来也与现场的星系群不同，它们提高了在中间环境中进行星系团预处理的可能性。 此外，随着样本量的增加，星系团合并的普遍性变得显而易见，这是一个分层宇宙的自然结果，在这个宇宙中，星系团代表了最大质量的维里化物体。 这个项目调查这些事件可能对星团星系群的影响-目前还没有很好地了解这些影响。结合最近完成的亚利桑那星团红移巡天（ACReS）-一个广泛的、恒星质量选择的、宽视场的光谱巡天-和现有的多波长数据，（从X射线到远红外），这个项目将研究星系团的等级增长与其重子成分演化之间的联系。 该项目的主要目标如下：（1）确定每个星系团的动力学状态，并将其与星系团星系群的整体性质联系起来，（2）通过识别星系团周围的环境和收集星系团周围的坠落星系团的独特样本来探测星系团周围的质量分布，（3）将坠落星系的性质与它们的局部环境联系起来，从而第一次在一个大的、统一的星系团样本中确定星系预处理的地点和必要条件。（1）调查人员将为ACReS项目创建一个针对广大受众的配套网站，突出使用多媒体技术，波长和光谱数据，以更深入地了解宇宙。 该网站将向当地学校教师大力宣传，供他们在课堂上使用。 (2)该项目将在Mt. Lemmon SkyCenter为K-14教师带来与亚利桑那大学天文学家的密切联系，并将科学发现的兴奋带入亚利桑那州南部的教室，少数民族占学生人数的70-80%。 (3)该项目将为ACReS集群构建一个数据库，该数据库将在两年期结束时向社区发布，为未来的集群研究创造遗产。 (4)首席研究员将培训本科生和博士后研究员。

Clusters of galaxies are key players in unraveling the mysteries behind galaxy formation and evolution, and understanding such mysteries is necessary to uncover how our Universe evolved and to learn how our own Milky Way Galaxy began. Galaxy clusters have long been considered active sites of galaxy evolution although the physical processes driving these transformations have yet to be established. Recent studies have revealed that, even at large distances from the cluster center, galaxy populations look different from those in the field, and they raise the possibility of cluster galaxy pre-processing in intermediate environments. Furthermore, as sample sizes have increased, the ubiquity of cluster mergers has become apparent, a natural consequence of a hierarchical universe where clusters represent the most massive virialized objects. This project investigates the effects that these events may have on the cluster galaxy population---effects that are currently not well understood.Combining the recently completed Arizona Cluster Redshift Survey (ACReS)---an extensive, stellar-mass selected, wide-field spectroscopic survey---with existing multi-wavelength data (from X-rays to far-infrared), this project will study the connections between a cluster's hierarchical growth and the evolution of its baryonic components. The project's main objectives are the following: (1) to determine each cluster's dynamical state and correlate this with global properties of the cluster galaxy population, (2) to probe the mass distribution surrounding the clusters by identifying filamentary environments and by compiling a unique sample of infalling groups around clusters, and (3) to relate infalling galaxy properties to their local environments, thereby identifying the sites and requisite conditions for galaxy pre-processing in a large, uniform sample of clusters for the first time.The broader impacts of this project include the following: (1) The investigators will create a companion web site for the ACReS project aimed at a wide audience that highlights the use of multi-wavelength and spectroscopic data for a deeper understanding of the Universe. The web site will be aggressively publicized to local school teachers for use in their classrooms. (2) The project will conduct workshops at the Mt. Lemmon SkyCenter for K-14 teachers to bring them into close contact with astronomers at The University of Arizona and bring the excitement of scientific discovery into Southern Arizona classrooms, where ethnic minorities make up to 70-80% of the student population. (3) The project will construct a database for ACReS clusters that will be released to the community at the end of the two year period to create a legacy for future cluster studies. (4) The principal investigator will train undergraduates and a postdoctoral researcher.