发表机构
Astronomical Institute, Tohoku University; Department of Astronomy, University of Tokyo; Center for the Early Universe, The University of Tokyo; Department of Physics, University of Bath; Department of Astronomy & Physics and Institute for Computational Astrophysics, Saint Mary’s University; School of Physics, HH Wills Physics Laboratory, University of Bristol; Institute for Cosmic Ray Research, The University of Tokyo; Department of Physics and Astronomy, School of Science, Kwansei Gakuin University; National Institute of Information and Communication Technologies（东北大学天文学研究所; 东京大学天文学系; 东京大学早期宇宙中心; 巴斯大学物理系; 圣玛丽大学天文与物理系及计算天体物理学研究所; 布里斯托大学HH威尔斯物理实验室物理学院; 东京大学宇宙线研究所; 关西学院大学理学部物理与天文学系; 信息通信研究机构）
机构由 AI 辅助整理，请以论文原文为准。AI 中文总结
本研究通过系统光谱观测确认了三个$z\sim3$原星系团，发现其成员星系性质各异，反映了原星系团发展阶段的不同，为理解星系团形成路径提供了重要样本。
AI 中文摘要
我们展示了三个$z\sim3$处原星系团候选体的后续光谱观测结果，这些候选体是通过Hyper SuprimeCam Subaru战略计划（HSC-SSP）的宽场成像中U型dropout星系的过密区域选取的。所有三个目标在三维空间（即天球上的$>4\sigma$过密度和红移空间中的$>98.4\\%$置信度）均表现出紧密聚集，这为真实原星系团提供了明确证据。由于这三个原星系团是通过相同的数据集和技术识别出来的，它们代表了在最小观测偏差下研究原星系团性质多样性的良好样本。尽管这三个原星系团的平均星系种群与场星系一致，但每个原星系团各自展现出彼此不同或与场星系不同的显著特征。在一个原星系团中，成员星系以较高的Ly$\alpha$等值宽度（$EW_0$）和仍然高度恒星形成的大质量成员星系而突出。相反，在另一个原星系团中，成员星系的Ly$\alpha$ $EW_0$系统性较低，显示出相对更受抑制的恒星形成。这些差异可归因于原星系团发展阶段的差异。如果淬灭星系的存在指示着更成熟的系统，那么具有更强Ly$\alpha$发射的星系可能在星系团形成的早期阶段更为普遍。本研究基于的统一搜寻原星系团的方法，使我们能够将宇宙正午起始时的观测差异与星系团形成历史的不同路径联系起来。
英文摘要
We present the results from follow-up spectroscopy of three protocluster candidates at $z\sim3$, selected as overdense regions of $U$-dropout galaxies in the wide-field imaging of the Hyper SuprimeCam Subaru Strategic Programme. All three targets exhibit tight clustering in three-dimensional space, i.e. on the sky ($>4σ$ overdensity) and in redshift ($>98.4\%$ confidence), making for clear evidence of genuine protoclusters. Since these three protoclusters are identified by the same dataset and technique, they represent a good sample to study the diversity of protocluster properties with minimal observational biases. Although the average population across the three protoclusters is consistent with field galaxies, each protocluster individually exhibits distinguishing properties from each other or from field galaxies. In one protocluster, member galaxies stand out by a higher Ly$α$ equivalent width ($EW_0$), and massive members that are still highly star-forming. In contrast, relatively more suppressed star formation appears in another protocluster where the Ly$α$ $EW_0$ of member galaxies is systematically lower. These variations can be attributed to differences in the developmental phase of protoclusters. If the presence of quenching galaxies indicates a more mature system, galaxies with stronger Ly$α$ emissions may be more prevalent in the earlier stages of cluster formation. The uniform approach to searching protoclusters on which this study builds enables us to link observed variations at the onset of cosmic noon to different pathways in the history of cluster formation.
Comments16 pages, 10 figures, 2 tables, accepted for publication in MNRAS
