Star Cluster Evolution: Near and Far, Large and Small, Old and Young

星团演化：近与远、大与小、老与年轻

• 批准号: RGPIN-2019-06570
• 负责人: Sills, Alison
• 金额: $ 2.99万
• 依托单位: McMaster University
• 依托单位国家: 加拿大
• 项目类别: Discovery Grants Program - Individual
• 财政年份: 2022
• 资助国家: 加拿大
• 起止时间: 2022-01-01 至 2023-12-31
• 项目状态: 已结题
• 来源: https://www.nserc-crsng.gc.ca/ase-oro/Details-Detailles_eng.asp?id=763093
• 关键词: Star; Cluster; Evolution; Near; Far

Star clusters are self-gravitating groups of stars with the same distance, age, and chemical composition. Stars are naturally formed in clustered environments, but only a few of those clusters will emerge as a self-contained, gravitatationally-bound entity from their natal molecular cloud. Nevertheless, the presence of close neighbours during the star formation process has important consequences for the masses and multiplicity of the stars that can form, and the survivability of planetary systems. Of those clusters that do emerge as clearly-identifiable objects, some will become massive old globular clusters. They have survived the entire galaxy formation process, including those times when two galaxies merged, or when a dwarf galaxy falls into its larger host galaxy. We can use the present-day properties of star clusters (size, mass, position, velocities, stellar content) to map galaxy structure and assembly over the last 10 billion years. But in order to use clusters to learn about star formation, planet formation or galaxy evolution, we need to understand how the clusters themselves form and change with time. The mature field of stellar dynamics (how stars move under their mutual gravity) provides many of the answers. However, stellar dynamics alone is not sufficient. It is important to also consider the interaction between the stars and star cluster with their external environment, such as the gas from which the stars formed, or the tidal field of the galaxy in which the cluster resides. The proposal describes a research program that will address these issues. In the next five years, we will concentrate on three specific projects: 1) to simultaneously and self-consistently model the formation and evolution of star clusters, their gas content, and their stellar populations, starting from the deeply embedded phase in molecular clouds, to produce the spherical, gas-free, open and globular clusters we see in the Milky Way today. 2) to trace the dynamical evolution of globular clusters and nuclear star clusters in their host galaxy, including episodes of galaxy mergers. In particular, we will quantify any observational signatures of accretion and merging on the individual clusters and the cluster populations as an ensemble. 3) to predict the expected observational signatures of the present-day massive old clusters as they are forming in the very early universe. Through simulations that combine stellar evolution, stellar dynamics, and hydrodynamics, we will produce a comprehensive picture of cluster formation and evolution on many scales of time, size, and distance.

星团是由距离、年龄和化学成分相同的恒星组成的自引力团。恒星是在星团环境中自然形成的，但只有少数星团会从它们出生的分子云中形成一个独立的、受引力约束的实体。然而，在恒星形成过程中，近邻的存在对可能形成的恒星的质量和多样性以及行星系统的生存能力有着重要的影响。在那些可以清晰辨认的星团中，有些会变成巨大而古老的球状星团。它们在整个星系形成过程中幸存下来，包括两个星系合并的时候，或者一个矮星系落入它更大的宿主星系的时候。我们可以利用星团现在的属性（大小、质量、位置、速度、恒星含量）来绘制过去100亿年的星系结构和组合。但为了利用星团来了解恒星形成、行星形成或星系演化，我们需要了解星团本身是如何形成和随时间变化的。成熟的恒星动力学领域（恒星如何在相互引力下运动）提供了许多答案。然而，仅靠恒星动力学是不够的。重要的是还要考虑恒星和星团与外部环境之间的相互作用，比如恒星形成的气体，或者星团所在星系的潮汐场。该提案描述了一个将解决这些问题的研究计划。在接下来的五年里，我们将集中在三个具体的项目上：1)同时和自我一致地模拟星团的形成和演化，它们的气体含量，以及它们的恒星数量，从分子云的深嵌阶段开始，产生我们今天在银河系中看到的球形、无气体、开放和球状星团。2)追踪其宿主星系中球状星团和核星团的动态演化，包括星系合并事件。特别是，我们将量化任何观测到的吸积和合并的特征在单个星团和星团人口作为一个整体。3)预测今天的大质量老星团在宇宙早期形成时的预期观测特征。通过结合恒星演化、恒星动力学和流体动力学的模拟，我们将在许多时间、大小和距离的尺度上产生星团形成和演化的全面图景。