Research Interests: Globular clusters, stellar populations, evolution of galaxies
William Harris and The Big Picture
My main research interests are in the earliest stages of galaxy evolution — the first few Gigayears of a galaxy’s history during which structures like its halo stars and globular clusters emerged. Their properties yield unique clues to the most active part of galaxy formation. See my webpage for more, but here’s a shortlist of projects I’m currently involved with:
Hubble Space Telescope imaging of a series of supergiant elliptical galaxies in the cosmologically “nearby” universe at distances from 40 to 200 Megaparsecs.¬† These giants have the largest globular cluster populations known (tens of thousands of clusters per galaxy) and with this data, our team is building up the biggest photometric database for globular clusters in existence.¬† With this material we are exploring patterns in the distributions of globular cluster luminosity, heavy-element enrichment, and spatial distributions in their galaxy halos — all of which are tracers of their formation epoch.
Correlations between globular cluster populations and other large-scale properties of their host galaxies, including dynamical mass, galaxy type, and (very puzzlingly) their central supermassive black holes.
Dynamics and assembly history of groups of galaxies over the redshift range z=0 to 1.
Photometry and modelling of the halo-star populations in nearby galaxies such as M33, NGC 5128, and M87.
Developing hydrodynamic modelling for the formation of massive star clusters.¬† The formation stage of “true” globular clusters (in the mass range of 0.1 to 10 million Solar masses) from their parent molecular clouds is the least well understood, but also most crucial, stage in their histories, and is likely to have produced important feedback on the larger-scale star formation history of the entire galaxy.
