Physical Origin of Globular Clusters in the Context of Galaxy Formation

球状星团（英语：Globular Clusters，GC）是由数十万颗恒星组成的致密球状星团，存在于大多数星系的晕中，通常包含一些星系中最古老和最贫金属的恒星。虽然GC自17世纪以来就被观察到，但它们的起源和在星系形成中的整体作用代表了长期存在的问题。该研究项目将进行一系列具有超高空间分辨率的最先进的宇宙流体动力学模拟，以直接测试贫金属GC的形成模型，该模型可以直接面对当前和不久的将来设施的观测，无论是在高红移还是在当前时代。该项目还将支持一名博士后研究人员，并继续努力为公众提供星系和GC模拟的计算机可视化。该项目的工作假设是，低金属丰度GC代表最初成核矮星系的剥离恒星核（即，不只是大的和其他普通的星星集群），形成的时代附近的再电离（EoR）。研究小组将通过以亚秒差距的空间分辨率运行许多宇宙学流体动力学模拟来探索这一想法，从EoR开始，这些模拟将成为当今星系的类似物，其晕质量为银河系的1.0，0.1和0.01。类似于年轻矮星系的富含气体的浓度将被标记及其随后的演化（星星形成、SNe反馈等）将被跟踪直到z = 6，之后它们将被视为无碰撞粒子并向前演化到当前纪元（z = 0）。观测来自一个统计上显着的模拟GC的样本，包括他们的运动学，银河系范围内的分布，化学丰度和分散作为银河系环境的函数，以及金属丰度和恒星质量之间可能的相关性。与当地低金属含量GC的比较将测试这种形成情景（例如，模拟的和真实的GC是否遵循相同的金属度-恒星质量关系？模拟也将允许有核矮星系的比例估计，以及使用JWST，阿尔马和其他facilities.This award的观测GC在EoR的可行性反映NSF的法定使命，并已被认为是值得通过使用基金会的智力价值和更广泛的影响审查标准进行评估的支持。

Globular Clusters (GCs) are dense spheroidal associations of hundreds of thousands of stars that are found in the halos of most galaxies, and which typically contain some of a galaxy's oldest and most metal poor stars. While GCs have been observed since the 1600's their origin(s) and overall role in galaxy formation represent longstanding problems. This research project will undertake a series of state-of-the-art cosmological hydrodynamical simulations with ultra-high spatial resolution to directly test a formation model of metal poor GCs that can be directly confronted by observations with current and near-future facilities, both at high redshift and in the current epoch. The project will also support a postdoctoral researcher as well as continuing efforts to provide computer visualizations of galaxy and GC simulations for the public.The working hypothesis of this project is that low metallicity GCs represent the stripped stellar nuclei of what were initially nucleated dwarf galaxies (i.e., not just big and otherwise ordinary star clusters) that formed near the epoch of re-ionization (EoR). The research team will explore this idea by running many cosmological hydrodynamic simulations at sub-parsec spatial resolution starting at the EoR of what will become the analogs of present day galaxies with halo masses of 1.0, 0.1, and 0.01 that of the Milky Way's. Gas rich concentrations that resemble young dwarf galaxies will be tagged and their subsequent evolution (star formation, SNe feedback, etc.) will be followed until z = 6, after which they will be treated as collisionless particles and evolved forward to the current epoch (z = 0). Observables derived from a statistically significant sample of simulated GCs include their kinematics, galaxy wide distributions, chemical abundances and dispersion as a function of galactic environment, and possible correlations between metallicity and stellar mass. Comparisons with local low metallicity GCs will test this formation scenario (e.g., do the simulated and real GCs follow the same metallicity-stellar mass relation?). The simulations will also allow estimates of the fraction of nucleated dwarf galaxies as well as the feasibility of observing GCs at the EoR using the JWST, ALMA and other facilities.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.