My main research focus is on "Galactic archaeology" - unwinding the present-day orbits and chemical compositions of stars in the Milky Way to study the processes at work early in Galactic history. I am one of two Project Scientists for the GALAH (Galactic Archaeology with HERMES) survey, which began in late 2013. Over a five-year observing program, we will use the HERMES spectrograph, together with the 2dF 400-fiber positioner, to take high-resolution spectra of 1 million stars in the Milky Way's disk and halo from the Anglo-Australian Telescope. We will determine abundances of up to 29 important chemical elements for each star, and plan to use this unprecedented data set to identify stars that originally formed together. Combining this with the precise positions and distances the ESA Gaia spacecraft will measure for all of our stars, we will study the history of star formation, chemical evolution, migration and minor mergers in the Galaxy.
In other work, I use moderate-resolution spectroscopy from Keck Observatory, Lick Observatory and the Very Large Telescope to study the compositions of stars in globular clusters, some of the oldest stars in the Milky Way, and to compare them to star clusters in nearby dwarf galaxies. Since globular cluster stars formed at the very beginning of our galaxy's lifetime, we can use their properties to reconstruct the early history of the Milky Way. Roughly half of the stars in globular clusters have an unusual abundance pattern in the "light" elements (carbon, nitrogen, oxygen, sodium, magnesium and aluminum), indicating that star formation in clusters in the early Galaxy happened quickly and involved recycling material between subsequent generations of stars.
Comparing the abundance patterns in Galactic globular clusters with the patterns in star clusters in nearby dwarf galaxies illuminates the ways in which the large-scale galactic environment affects star formation, and comparing old globular clusters to intermediate-age clusters allows investigation of the ways that cluster formation has changed between the early Universe and the present day. Star clusters that are forming now are quite different from what we think the early phases of globular clusters were like: less massive, generally located in the disks of galaxies, and not able to recycle material into multiple generations. This implies that there has been significant evolution between the early Universe and the present day in the way that star clusters are formed, and also that individual globular clusters have evolved strongly over that same time period.
- GALAH data exploration: Build tools to help classify and search the large and growing dataset from the GALAH (Galactic Archaeology with HERMES) survey. Any level of programming experience welcome.
- Rare stars in the Galaxy: Search for stars that have migrated from star clusters into the Galactic halo, or have captured material from a binary companion, using spectroscopy from the AAOmega Evolution of Galactic Structure survey.
- Star clusters and stellar abundances: A star's chemical abundance pattern is a record of where and when it formed. Investigate the differences between stars in clusters that are young and old, in the Milky Way and in nearby dwarf galaxies, to explore the effect of environment and time on star clusters.
You can find more information about these and other available research projects in the School of Physics on the Research Projects page.