Massive Star Clusters: Rethinking the Fundamentals

布罗迪博士和她的团队研究球状星团，这是比以前认为的更复杂的对象。这些相对孤立的自引力系统部分地屏蔽了影响星系形成和组装的许多因素，如合并，反馈和重子的能量流。因此，这些天体传统上被认为是由单一年龄和金属丰度的恒星组成的简单恒星群的代表。在这种假设下，球状星团的性质被用来在各种背景下放置约束，如恒星种群模型的校准，宇宙早期历史的计时器，以及星系形成的发光化石。然而，即使是孤立的，也有内部过程，例如化学元素的自我富集，这影响了球状星团的演化。这项工作的目标是了解球状星团如何以及为什么偏离了具有单一年龄和金属丰度的简单恒星群体的理想。该计划研究河外和银河系球状星团，并整合了从观测和理论建模中获得的化学和动力学约束。用多镜望远镜（MMT）、凯克望远镜和麦哲伦望远镜对单个球状星团进行光度和光谱观测，以获得质量与光的比值和丰度异常等数量，并研究年龄、金属丰度、初始质量函数、动力学演化和星团中演化恒星的反馈等因素。主要的努力是为大质量星星团之间的自我富集发展一个统一的设想;通过动力学和恒星人口调查更好地了解球状星团的恒星含量;并研究球状星团和星系之间的关系在球状星团质量函数的极端上限。球状星团的性质在天体物理学中有着广泛的意义;从球状星团中的恒星种群得出的推论为恒星的形成和演化理论提供了信息。这些反过来又对星系的组装历史和星系内暗物质的分布等问题产生影响。这项研究支持博士后研究人员的培训。该研究小组与国家非营利教育组织“科学伙伴”（Science Buddies）保持着持续的合作关系，该组织是K-12科学项目的在线资源。这里的研究结果将被纳入适合年龄的动手学习活动（主要通过科学博览会），以激励进一步的研究，并鼓励从事科学事业。

Dr. Brodie and her team study globular clusters of stars, which are more complicated objects than previously thought. These relatively isolated, self-gravitating systems are partially shielded from the many factors such as mergers, feedback, and energetic flows of baryons, which affect the formation and assembly of galaxies. Thus these objects traditionally were regarded as representative of simple stellar populations which consist of stars with a single age and metallicity. Under this assumption, globular cluster properties were used to place constraints in a variety of contexts such as calibrations for stellar population models, chronometers of the early history of the universe, and luminous fossils of galaxy formation. However, even while isolated, there are internal processes, such as self-enrichment in chemical elements, which influence the evolution of globular clusters. The goal of this work is understand how and why globular clusters deviate from the ideal of being simple stellar populations with a single age and metallicity. This program studies of both extragalactic and Galactic globular clusters, and integrates chemical and dynamical constraints obtained from observation and theoretical modeling. Photometric and spectroscopic observations of individual globular clusters with the Multiple-Mirror Telescope (MMT), and the Keck and Magellan telescopes are used to derive quantities such as the mass-to-light ratios and abundance anomalies, and to investigate factors such as age, metallicity, initial mass function, dynamical evolution, and feedback from evolved stars in the clusters. The major effort is to develop a unified scenario for self-enrichment among massive star clusters; to better understand the stellar content of globular clusters through dynamical and stellar population investigations; and to study the relationship between globular clusters and galaxies at the extreme upper limit of the globular clusters mass function. The properties of globular clusters have wide implications in astrophysics; inferences drawn from stellar populations in globular clusters inform theories of the formation and evolution of stars. These in turn have implications on issues such as the assembly histories of galaxies and the distribution of dark matter within galaxies.This research supports the training of a postdoctoral researcher. The research team has an ongoing partnership with the national, non-profit educational organization called Science Buddies, which is an online resource for K-12 science projects. Results from the research here will be incorporated into age-appropriate, hands-on learning activities (primarily through science fairs) to inspire further study and encourage taking careers in science.