Collaborative Research: Rethinking the Fundamentals of Massive Star Clusters

合作研究：重新思考大质量星团的基本原理

• 批准号: 1515084
• 负责人: Aaron Romanowsky
• 金额: $ 4.07万
• 依托单位: San Jose State University Foundation
• 依托单位国家: 美国
• 项目类别: Continuing Grant
• 财政年份: 2015
• 资助国家: 美国
• 起止时间: 2015-07-01 至 2019-06-30
• 项目状态: 已结题
• 来源: https://www.nsf.gov/awardsearch/showAward?AWD_ID=1515084&HistoricalAwards=false
• 关键词: Collaborative; Research; Rethinking; Fundamentals; Massive

A Globular Cluster is a tight group of hundreds of thousands of stars bound together by gravity. There are hundreds of Globular Clusters orbiting around our own Milky Way galaxy. Globular Clusters serve as fossils that trace conditions in the universe at the earliest times, when galaxies were just starting to form. Intriguing differences are observed between individual Globular Clusters, which provide clues about the formation of our Galaxy. In Globular Cluster stars, the concentrations of atoms belonging to different chemical elements vary in ways that challenge conventional wisdom about the ages, origins and life cycles of stars. The investigators will make observations with some of the world?s largest and best-equipped telescopes to test theoretical models of how stars, star clusters and galaxies come to be.The principal work involves (a) developing a unified scenario for self-enrichment among star clusters; (b) understanding the stellar content of Globular Clusters through novel dynamical and stellar population investigations; and (c) studying the relationship between Globular Clusters and galaxies at the extreme upper limit of the Globular Cluster mass function. New optical and near-infrared photometric and spectroscopic observations will be made to explore how measurable quantities (such as mass-to-light ratios and abundance anomalies) depend on age, metallicity, stellar initial mass function, and dynamical evolution. Intriguing trends, many of which confound standard interpretations, have already been identified: 1) self-enrichment appears to be implicated in abundance spreads in Galactic Globular Clusters and in a mass-metallicity relation found in extragalactic Globular Cluster systems; 2) observed properties of galaxy stellar halos, and initial measurements of gas in intermediate-age clusters, each challenge the favored mechanism for self-enrichment; 3) the dependence of mass-to-light ratio on metallicity is opposite to that expected from stellar evolution models; 4) an expanding zoo of compact stellar systems has been identified, including ultra compact dwarfs, that could be formed either by tidal stripping of dwarf galaxies or from Globular Cluster mergers; 5) the elevated mass-to-light ratios of ultra compact dwarfs may be explained by massive central black holes. The investigators will clarify each of these issues, test stellar evolution and population synthesis models, and trace the origins of compact stellar systems.Since Globular Clusters are more complex than formerly realized, understanding their properties and how they relate to other types of stellar systems has wide implications in astrophysics; inferences drawn from Globular Clusters inform theories of the formation and evolution of stars, galaxies, black holes, and dark matter. This fundamental work impacts forefront research from star formation to cosmology. To promote the broader impacts of this research effectively, the partnership with the non-profit organization, ?Science Buddies?, will be continued. This highly successful pilot program has already engaged thousands of K-12 students from diverse backgrounds, including disadvantaged groups. A vigorous program of professional and public outreach will continue, with a proven record of including women, undergraduates, and minorities in forefront research. A successful pilot program to involve undergraduates in Massive Clusters research will be expanded. Students and post-docs will receive excellent training with access to world-class facilities and to senior researchers, participating in all aspects of the research process. A user-friendly, legacy catalog of newly discovered compact stellar systems and their fundamental properties will be publicly available online.

一个球状簇是一组由重力结合在一起的数十万颗恒星的紧密组。我们自己的银河系围绕着数百个球状簇绕行。球状簇充当化石，最早的星系刚开始形成时，最早的时间在宇宙中追踪条件。在个体球状簇之间观察到了有趣的差异，这提供了有关我们银河系形成的线索。在球状簇恒星中，属于不同化学元件的原子的浓度以挑战恒星的年龄，起源和生命周期的传统智慧的方式有所不同。调查人员将与世界上最大，装备最佳的望远镜进行观察，以测试恒星，星形簇和星系如何出现的理论模型。 （b）通过新的动力学和出色的人口调查来了解球形簇的出色含量； （c）研究球状簇质量功能极端极限的球状簇和星系之间的关系。将进行新的光学和近红外光度和光谱观测，以探索可测量的数量（例如质量与光比和丰度异常）如何取决于年龄，金属性，出色的初始质量函数和动态进化。有趣的趋势（其中许多混淆了标准解释）已经被发现：1）自我增强似乎与银河系球状簇中的丰度差异有关，以及在乳层外球体集群系统中发现的质量金属关系； 2）观察到星系恒星光环的特性，以及中级群集中气体的初始测量，每种气体都挑战了自我增强的偏爱机制； 3）质量与光比对金属性的依赖性与恒星进化模型的预期相反。 4）已经确定了紧凑型恒星系统的动物园，包括超紧凑型矮人，可以通过潮汐剥离矮星系或来自球状簇合并而形成。 5）超紧凑矮矮人的质量与光的比率可以通过大量的中央黑洞来解释。研究人员将阐明这些问题中的每一个，测试恒星的进化和种群综合模型，并追踪紧凑型恒星系统的起源。因为球形群集比以前实现的更为复杂，了解它们的性质以及它们与其他类型的恒星系统如何在天体物体物体中具有广泛的影响；来自球状簇提出的推论将恒星，星系，黑洞和暗物质的形成和演变介绍为理论。这项基本工作影响了从恒星形成到宇宙学的最前沿研究。为了有效地促进这项研究的更广泛影响，将继续与非营利组织？科学伙伴？这项非常成功的试点计划已经与来自不同背景的数千名K-12学生接触，包括弱势群体。专业和公共宣传的剧烈计划将继续，并在最前列研究中拥有包括妇女，本科生和少数群体在内的可靠记录。将扩大一项成功参与大规模集群研究的试点计划。学生和职业生涯将获得出色的培训，并可以进入世界一流的设施以及参与研究过程各个方面的高级研究人员。新发现的紧凑型恒星系统及其基本属性的用户友好，旧的旧目录将在线公开获得。