Supernova-driven evolution of the first stars and galaxies




Ritter, Jeremy Steven

Journal Title

Journal ISSN

Volume Title



Heavy elements like carbon and oxygen are ubiquitous throughout the observed Universe yet only hydrogen, helium, and a few trace light elements are predicted to have been created in the Big Bang. Massive stars fuse light elements to form heavier elements during their brief lifetimes and die as supernova (SN) explosions that enrich the surrounding gas clouds. The chemical evolution history of a galaxy can be traced back through cosmic time from the highly enriched young stars like the Sun to the ancient, extremely metal-poor stars in the outer halo. This dissertation presents a series of high-resolution cosmological numerical simulations designed to explore the initial stages of SN-driven galactic evolution, from the collapse of the very first stars in unenriched dark matter halos to the formation of hot, enriched outflows in a first galaxy. These 3D hydrodynamical simulations of discrete, expanding SN remnants show that they were capable of enriching their host dark matter mini halos and the surrounding gas sufficiently to satisfy the theoretical minimum threshold required to form new low mass metal-enriched stars. Hydrodynamical biases skew our ability to trace the enrichment of individual stars back to a single progenitor SN, however there is hope that we can characterize the enrichment signature of the first stars from the elemental abundance trends observed in the most ancient, metal-poor stars. Primordial gas enriched by a single progenitor SN, assuming Type II-like yields, can have abundance ratios that fall within the parameter-space for the observed populations of extremely metal-poor stars. Finally, galactic outflows are a common feature found in the outer halos of star-forming galaxies. It has long been theorized that the combined effects of many SNe could be responsible for powering the supersonic velocities observed in these outflows. A pilot simulation is performed to explore the effects of a continuous succession of discrete SNe, exploding one at a time in a small starburst galaxy, the results of which will provide insights into the expected thermodynamic and spectroscopic features we might expect when future missions like the James Webb Space Telescope begin to unlock this era in our cosmic history.



LCSH Subject Headings