I am interested in the formation and evolution of galaxies over cosmic time via external and internal processes. I am currently leading research in three main areas: supernovae, galaxy surveys, and absorption-line systems.
Supernovae have a direct influence on the formation and evolution of galaxies by such means as arresting and inducing star formation, chemically enriching galaxies, and contributing to the ionization and expulsion of gas. I pioneered a technique to detect supernovae in high redshift galaxies and at distances far greater than has been previously achieved. I am using these supernovae to measure the form of the stellar initial mass function and to constrain galaxy processes. This research has also discovered a class of ultra-luminous supernovae that may be observational examples of the pair-instability process. Our most distant discoveries occurred when the universe was only about 10% its current age. Because the first generation of stars (Population III stars) are believed to result in pair-instability supernovae, we may be detecting the deaths of the very first stars!
The dark matter mass and merger histories of galaxies are powerful means to track the formation and evolution of galaxies. I conduct large, deep imaging and spectroscopic surveys at high- and intermediate-redshift and analyze high-resolution cosmological simulations to investigate the spatial distributions and mass of galaxy populations. This work has uncovered a surprising relationship between both the spectral features and kinematics of galaxies and their large-scale environment. These surveys have also revealed the effects of mergers and interactions, for example, the relationship between emission feature strength and galaxy separation.
Absorption-line systems provide the necessary gas to fuel initial and ongoing star formation in galaxies. However, discerning sightlines through coalescing proto-galaxy populations from sightlines through inflowing gas from the IGM or galaxy halo outflows is far from straightforward. I am involved in several projects aimed to characterize absorption systems illuminated by a background quasar or galaxy. Understanding gas consumption and expulsion and identifying fundamental absorber properties and their host galaxies is essential for a complete picture of galaxy formation and evolution.