I am currently the Crawford H. Greenewalt Chair and Director of The Observatories of the Carnegie Institution for Science in Pasadena, California. As Director I oversee our research campus in Pasadena as well as Carnegie’s Las Campanas facility in Chile. Las Campanas is the home of the two twin 6.5m Magellan telescopes and will be the home of the Giant Magellan Telescope.
Over my career as a professional astronomer, I have worked on a wide range of scientific problems including groups and clusters of galaxies, transients, active galactic nuclei, quasar absorption-line systems, X-ray binaries, gamma-ray bursts, dark matter, fast radio bursts, and the missing baryons problem. Much of my research has focused on groups of galaxies. Most galaxies occur in small groups including our own Milky Way. As a graduate student, I led the research team that first discovered the presence of a significant hot gas component in galaxy groups (see the press release here). This discovery revolutionized our understanding of these systems. In particular, it demonstrated the existence of large amounts of dark matter in groups. My later work has demonstrated that the group environment has a big impact on how galaxies evolve in time. More recently, I have been part of the team that discovered the first binary quasar system and the team that followed up of a fast radio burst for the first time.
I served as a scientific editor for The Astrophysical Journal from 2005 until 2011. I am also a frequent consultant for both NASA and NSF.
I have also led many of The Observatories’ outreach activities. In 2002, I created Carnegie’s first public lecture series. The Carnegie Astronomy Lecture Series is held each spring and draws hundreds of people to each lecture. Our annual Open House event provides an opportunity for the public to learn about our historic past and to see modern science in action. I am also the creator of the Discover Science Project, an innovative program that brings astronomy and other sciences directly to elementary and middle-school students in the Los Angeles area. This program involves the creation of special rooms dedicated to science. I work closely with many local foundations to support these outreach activities.