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Session 105 - Galaxies: Counts & Kinematics.
Display session, Saturday, January 10
Exhibit Hall,

[105.09] A Galactic Evolution Model: Chemical Evolution of CI, CII, and CO

C. Campbell, J. Bally (U. Colorado)

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 model uses low, intermediate, and high mass stars and includes 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.

\medskip 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. In general, infall models and models using higher sloped initial mass functions, (either an IMF with various slopes or a Salpeter IMF with x=1.7) produce better results, predicting metallicities and interstellar fluxes more consistent with current epoch estimates.

\medskip 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.

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Program listing for Saturday