Cosmological Small-Scale Structure: The Formation of The First Stars, Galaxies, and Globular Clusters.

[摘要] Though the majority of stars now live in large, massive galaxies, understanding theorigins of all galaxies ab initio requires fully comprehensive modeling of cosmologicalsmall-scale structure. In this thesis, I present a theoretical study of galaxy formation thatfocuses on low-mass halos. These halos are the sites for the formation of the first stars andgalaxies at high redshift, and they also they play a role in forming massive globular clustersin the outskirts of the Milky Way.I develop a physical model for Population III star formation and feedback, and implementedit into the Eulerian hydrodynamic Adaptive Refinement Tree (ART) code. Withthis code, I designed, performed, and analyzed a suite of cosmological simulations thatresolve the formation of the first stars and galaxies. I quantify the extent of the dynamicalsignatures Population III stars can impart on their host galaxies, and derive a characteristicmass threshold, 3 million solar masses, above which Population III stellar feedback is no longerdynamically significant over significant cosmic timescales.I measure the duration of time for which Population III stars are the dominant driversof feedback in the universe. Due to the inhomogeneous and patchy enrichment of the intergalactic medium, I find Population III stars can continue forming in some environmentswell after the end of the cosmic dark ages. However, in individual galaxies that are sufficiently massive, Population II star formation takes over soon after the efficient enrichment by a single pair-instability supernova. Globally, Population II is dominant at cosmic epochs later than redshift (z ~ 15).Finally, I construct a semi-analytical model for globular cluster formation in hierarchicalcosmology, and use it to demonstrate a plausible scenario for the formation of theMilky Way’s globular cluster system. My model is successful in matching both the metallicityand mass distributions of galactic globular clusters. In particular, the bimodal natureof the metallicity distribution is for the first time explained by the single mechanism of themerging of protogalaxies.

[发布机构] University of Michigan

[效力级别] Astronomy

[关键词] Galaxy Formation;Astronomy;Science;Astronomy and Astrophysics