Globular Cluster Systems: What have we learned and what's next?, Thomas Puzia (National Research Council, Canada)

Globular Clusters are the best approximations to simple stellar populations known to exist. Compared to the complex stellar population mix of the diffuse, i.e. unresolved light of their host galaxies, they offer at present the only way of measuring abundance distribution functions and formation histories of stellar populations in galaxies beyond the Local Group. Given that globular clusters exist in virtually every galaxy they can be used as tracer populations of star formation and assembly histories of their host systems. In my talk, I will present recent advance in modeling the chemical distributions functions of globular cluster systems in massive elliptical galaxies that appear to require an early and rapid formation and subsequent dissipationless hierarchical mass assembly. The comparison of model predictions with spectroscopic observations reveals, for the first time, the presence of at least two distinct enrichment epochs of ancient globular clusters. The chemical signatures of some of these clusters imply formation epochs which predate those of the vast majority of stars in massive elliptical galaxies and make them candidates for some of the first stellar generations in the Universe. I will briefly discuss these exciting results in the context of hierarchical galaxy formation. Illustrating the next-generation of stellar evolution computations and population synthesis models, I will explain new diagnostic tools and some of the multi-faceted follow-up observational tests that can be performed using current and future facilities that will greatly advance our understanding of the very early galaxy formation processes.