Subproject A8: Uncovering the Galactic Stellar Halo Build-Up Through Chemodynamics of Globular Clusters
Glenn van de Ven (MPIA), Eva K. Grebel (ARI), Norbert Christlieb (LSW)
Up to two thirds of the Galactic halo globular clusters may have been accreted as part of dwarf galaxies, as suggested by the bimodal age-metallicity relation of globular clusters. The properties of the globular clusters can tell us about the small host galaxies in which they formed based on empirical mass-metallicity relations. Globular clusters themselves may get disrupted in the Galactic potential, contributing their stars to the halo field population. If they are sufficiently massive to contain multiple stellar populations, they will contribute both first-generation stars (which are chemically indistinguishable from halo field stars) and second-generation stars (which are enriched in light elements and possibly helium). In the first funding period, we found (as part of subproject A3) that a small fraction of inner halo stars shows light element abundance anomalies that are only found in second-generation stars observed in GCs, enabling us to make a first crude estimate of the contribution of globular clusters to the halo field star component. This discovery led to the inception of the new subproject A8, in which these issues will be explored in more detail using both chemical tagging and Gaia phase space information.
In the second funding period, we want to elucidate (1) the dwarf galaxy contribution to the Galactic halo using globular clusters as tracers, and (2) quantify the globular cluster contribution to the field using the unique chemical signature of so-called second-generation stars. The properties of these stars also allow us to constrain models for the formation of multiple populations in globular clusters.