I work on a wide variety of topics in cosmology and extragalactic astronomy.  Much of my work concerns precision cosmological constraints from the measurement of the large-scale structure of the Universe.  Another major theme is the evolution of galaxies and their relation to their environment.  My work spans observations, theoretical astrophysics, and numerical simulations.

Please see my bio for recent focus areas.  Key collaborations presently include the Dark Energy Spectroscopic Instrument collaboration, the James Webb Space Telescope Near-Infrared Camera team, the Euclid Consortium, and our Abacus N-body code.

I previously served as the Director of the Sloan Digital Sky Survey III, which includes a major large-scale structure known as the Baryon Oscillation Spectroscopic Survey, as well as surveys of the stellar population of the Milky Way galaxy and a search for extra-solar planets.  


The Sloan 2.5-m Telescope at Apache Point Observatory