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Session 51 - Galaxy Evolution and the Intergalactic Medium.
Display session, Wednesday, June 10
Atlas Ballroom,
We calculate the gas-phase abundances of neutral carbon (CI), ionized carbon (CII), and carbon monoxide (CO) as functions of time and redshift. The analysis of the millimeter and sub-millimeter wavelength lines of these carbon species is a powerful probe for studying galactic evolution and cosmology. Our galactic models use low, intermediate, and high mass stars and include Type II supernovae, infall, and various star formation rates. The interstellar gas phase abundances of carbon and oxygen are computed as functions of the gas mass fraction. For models without infall, the gas phase abundance of carbon bearing species peaks when about 70% of the baryonic mass of a galaxy has been consumed by star formation. The models also predict a much higher oxygen abundance relative to carbon in the early ages of the galaxy.
The fraction of gas-phase carbon in CI, CII, and CO phases is then determined from models of photon-dominated regions. We include the attenuation of radiation by dust grains and self-shielding of CO to find the average column densities of CI, CII, and CO. Galactic evolution models with varying star formation rates, initial mass functions, and the effect of Hubble type are discussed. We investigate how star formation in energetic bursts as well as in more continuous rates affects the metallicity and molecular gas evolution. We also explore whether a time-dependent initial mass function, the addition of a Population III star formation era, is needed to produce the rapid enrichment seen in high redshift quasars.
