Metallicity-Dependent Galactic Isotopic Decomposition for Nucleosynthesis

TL;DR

This paper introduces a model for isotopic decomposition as a function of metallicity, based on nuclear astrophysics and observational data, to improve initial abundance assumptions in stellar nucleosynthesis models.

Contribution

It provides the first complete average isotopic decomposition model dependent on metallicity, fitted to observational data, enhancing initial conditions for nucleosynthesis simulations.

Findings

Type Ia supernovae contribute ~70% to solar Fe.

Type Ia onset occurs at [Fe/H] ≈ -1.2.

Model constrains astrophysical sources of isotopes.

Abstract

All stellar evolution models for nucleosynthesis require an initial isotopic abundance set to use as a starting point. Generally, our knowledge of isotopic abundances of stars is fairly incomplete except for the Solar System. We present a first model for a complete average isotopic decomposition as a function of metallicity. Our model is based on the underlying nuclear astrophysics processes, and is fitted to observational data, rather than traditional forward galactic chemical evolution modeling which integrates stellar yields beginning from big bang nucleosynthesis. We first decompose the isotopic solar abundance pattern into contributions from astrophysical sources. Each contribution is then assumed to scale as a function of metallicity. The resulting total isotopic abundances are summed into elemental abundances and fitted to available halo and disk stellar data to constrain the model's free parameter values. This procedure allows us to use available elemental observational data to reconstruct and constrain both the much needed complete isotopic evolution that is not accessible to current observations, and the underlying astrophysical processes. Our model finds a best fit for Type Ia contributing \simeq 0.7 to the solar Fe abundance, and and Type Ia onset occurring at [Fe/H]\simeq -1.2.