Galaxies have a voracious appetite for fuel — in this case, fresh gas — but astronomers have had difficulty finding the pristine gas that should be falling onto galaxies. Now, scientists have provided direct empirical evidence for these gas flows using new observations from the Hubble Space Telescope. The team led by Nicolas Lehner, research associate professor at the University of Notre Dame, is presenting its work today at the meeting of the American Astronomical Society in Long Beach, Calif.
The team’s observations using Hubble’s two ultraviolet spectrographs, the Cosmic Origins Spectrograph and the Space Telescope Imaging Spectrograph, show large quantities of cool gas with very low quantities of heavy elements in the gaseous cocoons surrounding modern galaxies. The lack of heavy elements indicates this gas in the circumgalactic medium of the galaxies has not been strongly processed through stars. The members’ work, “The Bimodal Metallicity Distribution of the Cool Circumgalactic Medium at zMarissa Gebhard at newsinfo.nd.edu on January 10, 2013.