I'm interested in galaxy evolution in the early universe - in particular, the physical properties of high-redshift galaxies. A major part of my thesis research involved leading a campaign of near-IR spectroscopy of galaxies at z~2 with the Magellan FIRE instrument in Chile (see results here). Recently, I have been studying large samples of local galaxies from the SDSS to understand the nature of galaxies at high redshift in greater detail (see this paper). My work in this area has had a significant impact on our understanding of the nature of evolving emission line ratios at high redshift.
I also work on the problem of estimating galaxy redshifts (i.e., distances) from a limited number of photometric observations, using state-of-the-art techniques from machine learning. Statistically robust redshift estimates to over a billion galaxies will be crucial for the weak lensing experiments to be performed by the cosmology missions Euclid and WFIRST. My work in this area (see this paper) has helped define the spectroscopic needs of Euclid and WFIRST, and is the basis of a large Keck survey currently underway to obtain the needed spectra with DEIMOS, LRIS, and MOSFIRE. This effort, named the "Complete Calibration of the Color-Redshift Relation" (C3R2) survey, is a joint effort between NASA, Caltech, University of California, and University of Hawaii to map the empirical color-redshift relation of galaxies. The survey has currently been awarded 26.5 nights.