The Enigmatic (but Not Empty) Space Between Galaxies
Using powerful telescopes, we have now measured the distribution of galaxies from a time less than a billion years after the Big Bang. However, all of the stars in all of the galaxies account for a mere 6% of the “normal” (not dark) matter in the present-day universe. To search for the remaining normal matter, astronomers have designed experiments sensitive to an extremely diffuse phase of gas: using spectroscopy of bright background light sources (e.g., quasars), we identify foreground clouds of gas in absorption and count the number of atoms of various chemical elements they contain. I will present results from recent studies using this technique that reveal a massive reservoir of diffuse gas extending hundreds of kiloparsecs from galaxies like our Milky Way. I will then describe evidence demonstrating that the galaxies themselves play an important role in filling these reservoirs by driving large-scale flows of material away in so-called “galactic winds”. These results imply that most bright galaxies are surrounded by a dynamic gaseous halo containing at least as much normal matter as all of the stars and nebulae in the galaxies’ disks.
Kate Rubin, Ph.D., is an astronomer specializing in galaxy formation and evolution, with a particular emphasis on the physics of large-scale flows of gas through distant galaxy environments. This research makes extensive use of large ground-based optical telescopes, including the Magellan and Very Large Telescopes in Chile and the Keck Telescopes in Hawaii, as well as the latest generation of the Sloan Digital Sky Survey (SDSS-IV). Rubin uses these tools to study how energy produced by supernovae drives material from star-forming regions into galaxies’ surroundings, and to characterize the signatures of the accretion of gas onto galactic disks over the past eight billion years of cosmic time.
Dr. Rubin earned a B.S. in Physics and Astronomy from Yale University in 2004, and obtained her Ph.D. in Astronomy and Astrophysics from the University of California, Santa Cruz in 2010. She has held postdoctoral fellowship appointments at the Max Planck Institute for Astronomy in Heidelberg, Germany, and at the Harvard-Smithsonian Center for Astrophysics in Cambridge, MA. She joined the faculty in the Department of Astronomy at San Diego State University in 2016.
"What's Up?" in this month will be presented by John Garrett from TVA