On the Ionization and Chemical Evolution of the Intergalactic Medium

264 p.Thesis (Ph.D.)--University of Illinois at Urbana-Champaign, 2005.In the second part of this work, we address topics on the metal enrichment of the IGM. An overview of the current research in the cosmic metal evolution is provided in Chapter (5). In Chapter (6), we investigate the pre-enrichment of the IGM by parametrizing the metal abundance as dependent on the local baryon mass. We show that the UVB is an important bias because it preferentially keeps carbon ionized at the CIV state in the Lyalpha forest mass range. In Chapter (7), we explore whether metal feedback from Population III stars (z ∼ 15) alone explains the metal abundance and distribution at later redshifts. This idea is expanded in Chapter (8), by including an additional feedback from Population It stars formed in dwarf galaxies at redshifts z ≲ 10. We conclude that, the PopIII metals alone are insufficient to explain the detected levels of metal enrichment in the observable Universe. We find that at late redshifts a significant portion of the primordial metal component was transported into the voids. Therefore, signatures in transmission spectra from such regions would sample the primordial metals.U of I OnlyRestricted to the U of I community idenfinitely during batch ingest of legacy ETD