Contact
smartell@aao.gov.au
Australian Astronomical Observatory
105 Delhi Rd
North Ryde, NSW 2113
Australia
+61 (02) 9372 4885
Sarah Martell
I am a Research Fellow working at the Australian Astronomical Observatory in Sydney, Australia. I work in "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 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 elements carbon, nitrogen, oxygen, sodium, magnesium and aluminum, indicating that star formation in clusters in the early Galaxy happened quickly and at high density.
I am also the Project Manager for observations on the GALAH (Galactic Archaeology with HERMES) survey team. We will use the HERMES being built by the AAO, together with the 2dF 400-fiber positioner, to take high-resolution spectra of 1 million stars in the Milky Way's disk. We will determine abundances of at least 15 important chemical elements for each star, and plan to use this unprecedented data set to identify stars that originally formed together, and to investigate their subsequent migration in the Galaxy.
As a postdoctoral researcher at the University of Heidelberg, which is a partner in the Sloan Digital Sky Survey, I searched through the SEGUE database of moderate-resolution spectra for stars with globular cluster-like abundance patterns in the extended stellar halo of the Galaxy, in order to understand how much of the halo is made up of dissolved star clusters. I am currently expanding on that work, using high-resolution spectroscopy from the Hobby-Eberly Telescope and Keck Observatory to get a clearer picture of the elemental abundances in these rare immigrant stars.