Research

 My research focuses on the high-redshift Universe, particularly the evolution of the intergalactic medium (IGM), which contains most of matter in the Universe.  High-resolution quasar spectra, together with numerical simulations, have demonstrated that the IGM is arranged in a "cosmic web" of filaments and voids, with galaxies forming in the densest regions. I use quasar spectra to try and understand how the IGM evolves with time, and how galaxies and the IGM interact.  In particular, I study the processes by which hydrogen in the IGM is reionized by the first galaxies (we believe) and helium is reionized by quasars.  Recent projects have included charting the thermal history of the IGM, searching for the chemical signatures of the first galaxies, and measuring the total output of ionizing photons from all galaxies and quasars.

Career

PhD, California Institute of Technology

Postdoctoral Researcher, Carnegie Observatories

Kavli Fellow, Kavli Institute for Cosmology, Cambridge

PhD, California Institute of Technology

Postdoctoral Researcher, Carnegie Observatories

Kavli Fellow, Kavli Institute for Cosmology, Cambridge