MATs (Monday Afternoon Talks), 09/25/2023 — Speakers: Adriana Dropulic & Madeleine McKenzie

Monday September 25, 2023 3:00 pm

MATs (Monday Afternoon Talks)

3:00pm – 3:30pm, Adriana Dropulic
StreamGen: Morphologies and orbits of semi-analytic satellite galaxies
Stellar streams are excellent probes of dark matter halos and their structure. Interestingly, the Milky Way’s stellar streams are significantly more clustered in the inner regions of the Galaxy compared to those in simulations. These simulations are expensive and can differ substantially from the Milky Way in terms of host properties and assembly history, so it is difficult to ascertain if this disagreement is because of simulation properties, modeling, or statistics. In contrast, semi-analytic galaxy simulations are an efficient way to generate large, statistical samples of Milky Way-like galaxies, but do not contain particle-level information. We apply a theoretical model of stream formation to satellites generated by a semi-analytic galaxy simulation, SatGen, to identify distinct populations of stellar streams. We separate streams from shell-like structures and intact satellites in a suite of 2,000 semi-analytic galaxies with varying mass, feedback model, and disk properties. We show that the stream orbits can be substantially impacted by changing these properties, which stresses the importance of modeling them accurately in simulations.

3:30pm – 4:00pm, Madeleine McKenzie
Nucleosynthesis at the isotopic level: How Mg isotope ratios challenge our view of globular clusters and dwarf galaxies
In the context of hierarchical galaxy assembly, both globular clusters and dwarf galaxies serve as indispensable probes of the formation of our Milky Way. The chemical composition of stars within these ancient structures plays a pivotal role in constraining their chemical enrichment history. Each possesses its own chemical peculiarities; for instance, dwarf galaxies contain stars with low [alpha/Fe] compared to Galactic halo objects at the same metallicity. Meanwhile, globular clusters house multiple stellar populations characterized by their light element abundances. To date, most studies have focused almost exclusively on elemental abundances, however, nucleosynthesis operates at the isotopic level. In this talk, I will discuss how Mg isotope ratios shed light on both the accreted dwarf galaxy component of our Milky Way and the light element enhanced populations within globular clusters. This reveals contributions from SNeII and AGB stars that cannot be discerned through element abundances alone.


Hosts: Minghao Yue, Daniele Michilli


  • Adriana Dropulic, Princeton University
  • Madeleine McKenzie, Australian National University