Environmental effects at early cosmic times: galaxy evolution in the first massive clusters

这个项目是基于最近获得的，用HST和Spitzer对在z&gt；~1.4处通过Sunyaev-Zeldovich效应在2500平方度上探测到的五个高意义(S/N&GT；5)星系团的完整样本进行的深度、均匀的成像跟踪。SPT-SZ的大调查面积和深度使我们能够在这个宇宙时代已知的最稀有、最大质量的星系团中识别出这个仍然独特的星系团样本。星系团的选择与星系团质量密切相关，完全独立于星系团星系(不像大多数星系团调查在这些红移)，使这个样本独特地适合于无偏见的星系种群研究，探索早期星系团环境中星系演化的环境特征。我们设计了HST和Spitzer观测的具体组合，以提供第一个“基本数据集”，以开始有效地探测星系群，包括恒星的形成和猝灭，恒星质量组装，被动部分与恒星质量，红色序列的形成，最亮星系团的形成和演化，形态与恒星群性质，膨胀星系和盘状星系的结构演化，这些极端环境中的合并率和性质，以及在z~1.5的大多数质量晕中的星系恒星质量函数，晕占据分布和恒星质量分数。所有的HST和Spitzer观测现在都完成了，并且减少了。第一批分析正在进行中，DLR支持的计划侧重于HST观测，确认了这些星系团的高红移性质，从(完全独立的)红序列和X射线模拟分析中，最远的系统被一致地估计为z~1.8。在这次红移时，它不仅是SPT-SZ调查中发现的最远的星系团，也是迄今为止发现的最远的大质量(M500和GT；10^14 MSun)ICM选择的星系团，并且可能是在这个极端质量范围内已知的最远的星系团，而不考虑选择。我们在此请求支持继续这项工作，特别是充分利用HST和Spitzer观测之间的协同作用，这对本次研究的目标至关重要。拟议的项目将使我们能够完成对这种定义明确、均匀的大规模遥远星系团样本的首次研究，并利用其试点项目的性质，为新的和即将到来的调查(SPTPoll、SPT-3G、eROSITA)的星系演化研究有效地设计远程星系团的后续跟踪，连接目前最先进的工作及其强大的未来扩展。

This project is based on recently obtained, deep, homogeneous imaging follow-up with HST and Spitzer of the complete sample of five high-significance (S/N>5) galaxy clusters at z>~1.4 detected through the Sunyaev-Zeldovich effect in the SPT-SZ survey over 2500 square degrees. The large survey area and depth of SPT-SZ allow the identification of this still unique sample of clusters among the rarest, most massive known at this cosmic epoch. The cluster selection, tightly related to cluster mass and totally independent of cluster galaxies (unlike most cluster surveys at these redshifts), makes this sample uniquely suited for unbiased galaxy population studies probing environmental signatures on galaxy evolution in early cluster environments. We designed the specific combination of HST and Spitzer observations to provide a first "essential data set" to start efficiently probing galaxy populations in terms of star formation and quenching, stellar mass assembly, passive fractions vs. stellar mass, formation of the red sequence, formation and evolution of Brightest Cluster Galaxies, morphologies vs. stellar population properties, structural evolution of bulge- and disk-dominated galaxies, and merger rates and properties in these extreme environments, as well as the galaxy stellar mass function, halo occupation distribution and stellar mass fraction in most massive halos at z~1.5. All HST and Spitzer observations are now completed and reduced. First analyses are ongoing with a DLR-supported program focused on the HST observations, confirming the high-redshift nature of these clusters, with the most distant system being consistently estimated at z~1.8 from both the (totally independent) red-sequence and X-ray modeling analyses. At this redshift, it is not only the most distant cluster discovered in the SPT-SZ survey, but the most distant massive (M500>10^14 Msun) ICM-selected cluster discovered thus far, and potentially the most distant cluster known in this extreme mass range irrespective of selection. We ask here for support for continuing this work, in particular fully exploiting the synergy between HST and Spitzer observations which is critical to the goals of this investigation.The proposed project will allow us to complete the first study of this kind of such a well defined, homogeneous massive distant cluster sample, and exploit its pilot-project nature for an efficient design of follow-up of distant clusters for galaxy evolution studies for new and coming surveys (SPTpol, SPT-3G, eROSITA), bridging today's state-of-the-art work and its powerful future extensions.