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The chemical evolution of star-forming galaxies

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Item Summary

Title: The chemical evolution of star-forming galaxies
Authors: Zahid, Harus
Keywords: metallicity
Issue Date: Aug 2014
Publisher: [Honolulu] : [University of Hawaii at Manoa], [August 2014]
Abstract: The gas-phase oxygen abundance, i.e. metallicity, of a galaxy is set by the interplay between star formation and gas flows. Metals are dispersed into the interstellar medium by stellar winds and supernovae. Metals accumulate in the interstellar medium of starforming galaxies and provide a record of star-formation. However, inflows of unenriched gas into galaxies and metal-rich outows of gas from galaxies can both reduce the metallicity. Thus, measurements of the metallicity across cosmic time provide important constraints for understanding the cycling of gas through galaxies as they build their stellar mass and evolve. I have measured the chemical evolution of galaxies over the last 10 billion years of cosmic time. These measurements provide a coherent picture of how galaxies enrich as they build their stellar mass. Using these measurements, I have conducted the first census of oxygen in star-forming galaxies. The oxygen census reveals that over their lifetime, star-forming galaxies expel a substantial fraction of the oxygen they produce in outflows. The mass of oxygen missing from galaxies provides one of the most robust empirical constraints for the total mass lost via outflows in galaxies. I show that the amount of mass loss currently implemented in theoretical models is 1-2 orders of magnitude larger than the empirical estimates for mass loss from the oxygen census. The discrepancy between empirical and theoretical constraints for the amount of mass loss has important implications for our understanding of galaxy evolution. I conclude with a model that suggests that the chemical evolution of star-forming galaxies is very simple. The metallicity of star-forming galaxies for z 1:5 only depends on the stellar-to-gas mass ratio. The relation between metallicity and stellar-to-gas mass ratio is an universal relation followed by all galaxies as they evolve.
Description: Ph.D. University of Hawaii at Manoa 2014.
Includes bibliographical references.
Rights: All UHM dissertations and theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission from the copyright owner.
Appears in Collections:Ph.D. - Astronomy

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