The Evolution Of Carbon, Sulphur, and Titanium Isotopes from High-Redshift to the Local Universe

TL;DR

This study uses galactic chemical evolution models to analyze isotopic patterns of carbon, sulphur, and titanium from high-redshift to the present, challenging some existing assumptions and highlighting the need for model revisions.

Contribution

It provides new insights into isotopic evolution, testing claims about the roles of novae and initial mass functions, and compares model predictions with recent observational data.

Findings

Novae are not necessary for 12C/13C evolution in the solar neighborhood.

A massive star-biased initial mass function fits high-redshift sulphur data but predicts unlikely metallicities.

Titanium isotope predictions do not match observed trends, suggesting model revisions are needed.

Abstract

Recent observations of carbon, sulphur, and titanium isotopes at redshifts z~1 and in the local 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 GEtool, we have examined the evolution of these isotopes within the framework of a Milky Way-like system. We have three aims in this work: first, to test the claim that novae are required, in order to explain the carbon isotope patterns in the Milky Way; second, to test the claim that sulphur isotope patterns at high-redshift require an initial mass function biased towards massive stars; and third, to test extant chemical evolution models against new observations of titanium isotopes that suggest an anti-correlation between trace-to-dominant isotopes with metallicity. 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 12C/13C in the solar neighbourhood; a massive star-biased initial mass function is consistent with the low ratios of 12C/13C and 32S/34S seen in one high-redshift late-type spiral, but the consequent super-solar metallicity prediction for the interstellar medium in this system seems highly unlikely; and 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 the associated supernovae nucleosynthetic yields) may need a substantial overhaul to be made consistent.