Understanding the abundance spread in star clusters

Stars in the same star cluster vary in their chemical compositions by a surprisingly small amount - their abundances of heavy elements are usually identical to within a few percent. The goal of this project is to understand why this occurs, and to explore the extent to which it might be possible to use this homogeneity as a tool in galactic archaeology.

Preliminary simulations (a snapshot of which is shown - see http://adsabs.harvard.edu/abs/2014Natur.513..523F for the paper, or https://sites.google.com/a/ucsc.edu/krumholz/movies for the movie) suggest that star-forming gas is mixed by turbulence as the stars assemble. This plausibly homogenises the abundances. However, these calculations started from highly idealised initial conditions. The goal of this project is to remove that limitation, by following the flow of heavy elements starting on galactic scales and then following the gas it collapses to individual star clusters and stars.

The student will work with Prof. Krumholz to design and run simulations using the enzo adaptive mesh refinement code. These simulations will start with isolated, Milky Way-like galaxies, and will follow the flow of heavy elements as they are produced by supernovae, ejected into the ISM, and eventually re-incorporated into a new generation of stars. In addition to providing a direct answer to the question “why are star clusters homogeneous?”, this work will allow us to quantify the expected spread in abundances across stars that are born nearby but not necessarily in the same star cluster, a crucial unknown when it comes to the suitability of chemical abundance modeling as a tool for stellar archaeology.

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