The Evolution of Isotope Ratios in the Milky Way Galaxy
  Isotope ratios have opened a new window into the study of the details of
stellar evolution, supernovae, and galactic chemical evolution. We present the
evolution of the isotope ratios of elemental abundances (from C to Zn) in the
solar neighbourhood, bulge, halo, and thick disk, using chemical evolution
models with updated yields of Asymptotic Giant Branch (AGB) stars and
core-collapse supernovae. The evolutionary history of each element is different
owing to the effects of the initial progenitor mass and metallicity on element
production. In the bulge and thick disk the star formation timescale is shorter
than in the solar neighbourhood, leading to higher [alpha/Fe] ratios. Likewise,
the smaller contribution from Type Ia supernovae in these regions leads to
lower [Mn/Fe] ratios. Also in the bulge, the abundances of [(Na, Al, P, Cl, K,
Sc, Cu, Zn)/Fe] are higher because of the effect of metallicity on element
production from core-collapse supernovae. According to our predictions, it is
possible to find metal-rich stars ([Fe/H]>-1) that formed in the early Universe
as a result of rapid star formation. The chemical enrichment timescale of the
halo is longer than in the solar neighbourhood, and consequently the ratios of
[(C, F)/Fe] and 12C/13C are higher owing to a significant contribution from
low-mass AGB stars. While the [alpha/Fe] and [Mn/Fe] ratios are the same as in
the solar neighbourhood, the [(Na, Al, P, Cl, K, Sc, Cu, Zn)/Fe] ratios are
predicted to be lower. Furthermore, we predict that isotope ratios such as
24Mg/25,26Mg are larger because of the contribution from low-metallicity
supernovae. Using isotopic ratios it is possible to select stars that formed in
a system with a low chemical enrichment efficiency such as the satellite
galaxies that were accreted onto our own Milky Way Galaxy.
