Physical Origin of Globular Clusters in the Context of Galaxy Formation

点击翻译按钮获取中文摘要

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.