The evolution of isotoipc abundances from high-redshift to the local universe
Recent observations of carbon, sulphur, and titanium isotopes at redshifts z-.1 and in the Galactic stellar disc and halo have opened a new window into the study of isotopic abundance patterns and the origin of the chemical elements. Using our Galactic chemical evolution code CEtool, we have examined the evolution of these isotopes within the framework of a Milky Way-like system. We have three aims in this thesis: first, to test the claim that novae are required, in order to explain the carbon isotope patterns in the Milky Way (Romano & Matteucci 2003); second, to test the claim that sulphur isotope patterns at high-redshift require an initial mass function biased towards massive stars (Muller et al. 2006); and third, to test extant chemical evolution models against new observations of titanium isotopes that suggest an anti-correlation between trace-to-dominant isotopes and metallicity (Chavez 2008). Based upon our dual-infall galactic chemical evolution modelling of a Milky Way-like system, and the subsequent comparison with these new and unique datasets, we conclude the following: novae are not required to understand the evolution of 12 C/ 13 C in the solar neighbourhood; a massive star-biased initial mass function is consistent with the low ratios of 12 C/ 13 C and 32S/34 S seen in one high-redshift late-type spiral, but the consequent supersolar metallicity prediction for the interstellar medium in this system seems highly unlikely; deficient isotopes of titanium are predicted to correlate positively with metallicity, in apparent disagreement with the new datasets; if confirmed, classical chemical evolution models of the Milky Way (and/or the associated supernovae nucleosynthetic yields) may require amendment to be made consistent.
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