J. Colin Hill is a postdoctoral researcher in the astronomy department at Columbia University. He attended college at the Massachusetts Institute of Technology, where he studied physics and mathematics. He then spent a year studying theoretical physics at Cambridge before starting his Ph.D. in astrophysics at Princeton in 2009.
His research is focused on the cosmic microwave background (CMB), which is the remnant thermal radiation left over from the Big Bang that still permeates the universe today. Using data from the Atacama Cosmology Telescope and the Planck satellite, he studies physical processes that affect CMB photons as they travel to us over cosmic time. These include gravitational lensing, in which a photon’s path is bent by the gravity of intervening structures, and the Sunyaev–Zel’dovich effect, in which a photon’s energy is changed by an encounter with hot, ionized gas. He showed for the first time that the Sunyaev–Zel’dovich and lensing signals in the CMB are correlated, indicating that the hot, ionized gas traced by the former follows the dark matter traced by the latter. This result provides an important foundation for future studies that aim to use the distribution of massive galaxy clusters — where most of the hot, ionized gas is found — to constrain the properties of dark matter, dark energy and the initial conditions of the universe.