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Magnesium isotopes as a probe of the Milky Way chemical evolution

Anders Overaa Thygesen

Research into the chemical evolution history of the Milky Way has seen a renewed interest over the last decade, with the advent of several large-scale spectroscopic surveys like SDSS-SEGUE, Gaia-ESO and APOGEE, to name a few. Whereas these surveys have already provided impressive
results, they only provide bulk elemental abundance measurements. Isotopic abundances are much more observationally challenging to obtain, and can only be measured for a few elements. Nevertheless, in the cases where one can obtain isotopic abundance measurements, we can get additional insight into the preceeding nucleosynthesis, complementary to what elemental
abundances can deliver.

Isotopes of magnesium are particularly interesting, as the different isotopes are produced in different nucleosynthesis sites, active on different timescales. As such, they are a very useful probe for the enrichment timescale of a stellar population.

In this talk I will present the first measurements of Mg isotopes in giant stars in the globular cluster 47 Tucanae, as well as in the inner part of the Milky Way disk and the bulge. I will discuss the impact of the first application of 3D stellar atmospheric models to the spectral synthesis.
The isotopic distribution of Mg, measured from the molecular MgH features, will be discussed in the context of the multiple population phenomenon for 47 Tucanae. For the stars in the inner disk and the bulge, the results will be used to put additional constraints on the proposed bulge-disk
connection and the formation history of the bulge.