Wednesday, March 28, 2012

1203.5969 (Christopher West et al.)

A Phenomenological Model for Isotopic Galactic Chemical Evolution    [PDF]

Christopher West, Alexander Heger
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 galactic chemical evolution 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 decompose the isotopic solar abundance pattern into contributions from astrophysical sources. Each contribution is then assumed to evolve as a function of metallicity. The resulting total isotopic evolution is summed into an elemental evolution 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 that Type Ia contributed 70.8 % to the solar Fe56 abundance, and that the onset of Type Ia occured at [Fe/H]=-1.184.
View original: http://arxiv.org/abs/1203.5969

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