Globular Cluster Systems in Extreme Environments: Origins and History

球状星团是密度大、质量大、受引力约束的星团，普遍存在于所有大型星系中。它们是最古老的恒星系统之一，形成于宇宙历史的前几个千禧年，来自早期星系中密度最大、质量最大、最猛烈的恒星形成地点。尽管在今天的宇宙中，GC只占星系中所有恒星质量的1%或更少，但它们在追踪恒星和银河系演化过程中发挥着关键作用。我的研究建议针对三条这样的道路： (1)在丰富的星系团中，在星系之间的广阔空间中也发现了球状星团，这些星际GC的特征以一种独特的方式追溯了星系团中星系之间相互作用和相遇的历史。为了追求这一新的前沿，我正在领导一个新的观测项目，使用哈勃太空望远镜和斯巴鲁望远镜对丰富的英仙座星系团中的星系际GC种群进行全面调查。 (2)球状星团的数量最多的是最大的星系：最亮的星系团(BCG)。这些星系通过吸收周围较小的卫星星系一直生长到今天，但环境对这些巨型星系演化的影响并不完全清楚。它们的GC种群拥有关于它们早期历史的独特线索，因为GC具有强烈依赖于它们起源的星系类型的特性。作为我正在进行的研究巨型星系GC系统计划的一部分，我们将使用我们来自哈勃太空望远镜的新数据来系统地调查整个巨大环境中的BCG，以找出这些星系生长的速度有多快，以及哪些类型的星系对它们的生长和组装做出了贡献。这项工作将填补宇宙中最大星系起源之谜的一大块。 (3)一个众所周知的新发现是，一个球状星团内可能有多个恒星群，它们的年龄相同，但轻元素的比例不同。目前的观测很好地证实了它们的存在，但很难理解它们是如何在如此小的(以银河系标准)恒星系统中出现的。关于这种效应的起源，目前的观点存在争议。基于我们以前的一位博士生的理论工作，我们将追踪星系团中最早的大质量恒星对其形成气体的内部丰度混合的影响。这是一个很有希望的和令人兴奋的新途径，以了解多个种群的起源，坚实地基于我们的严格和定量的星团形成理论。这项工作有可能影响该社区对早期宇宙中大质量星团形成的研究方向。

Globular clusters are dense, massive, gravitationally bound clusters of stars that are found universally in all large galaxies. They are among the oldest stellar systems, having formed in the first few Gigayears of the universe's history, out of the densest, most massive, and most violent star-forming sites within early galaxies. Although in the present-day universe GCs make up just a percent or less of all stellar mass in galaxies, they play key roles for tracing a huge range of processes in stellar and galactic evolution. My research proposal aims at three such paths: (1) In rich clusters of galaxies, globular clusters are also found in the vast space between the galaxies, and the characteristics of these intergalactic GCs trace, in a unique way, the histories of interactions and encounters among the galaxies in the cluster. To pursue this new frontier I am leading a new observational program with the Hubble Space Telescope and with the Subaru telescope for a comprehensive survey of the intergalactic GC population in the rich Perseus cluster. (2) The largest numbers of globular clusters are found in the largest galaxies: the Brightest Cluster Galaxies (BCGs). These galaxies grow right up to the present day by absorbing the smaller satellite galaxies around them, but the effects of environment on the evolution of these giant galaxies are not completely understood. Their GC populations hold unique clues to their early history, because GCs have properties that depend strongly on the type of galaxy they originated in. As part of my ongoing program to study the GC systems in giant galaxies, we will use our new data from the Hubble Space Telescope to systematically survey BCGs over their entire huge range of environments to find out how quickly these galaxies grew, and what types of galaxies contributed to their growth and assembly. This work will fill in a major piece of the puzzle for the origin of the largest galaxies in the universe. (3) A well known new discovery is that a single globular cluster may have within it multiple stellar populations that all have the same age but different ratios of the light elements. These are well established by current observations to be present, but it has been difficult to understand how they arose in such small (by galactic standards) stellar systems. Current ideas for the origin of this effect are controversial. Building on theoretical work by one of our former PhD students, we will trace the effects of the earliest massive stars in the cluster on the internal abundance mixture of its star forming gas. This is a promising and exciting new avenue for understanding the origin of multiple populations, based solidly on our rigorous and quantitative theory for star cluster formation. This work has the potential to shape the community's direction of research into the formation of massive star clusters in the early universe.