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1996ApJ...456L...5M HIGH-IONIZATION QUASAR ABSORPTION LINES: A TEST OF THE EXISTENCE OF HOT GAS IN SPIRAL-RICH GROUPS JOHN S. MULCHAEY The Observatories of the Carnegie Institution of Washington, 813 Santa Barbara Street, Pasadena, CA 91101 RICHARD F. MUSHOTZKY NASA/Goddard Space Flight Center, Laboratory for High Energy Astrophysics, Code 666, Greenbelt, MD 20771 DAVID BURSTEIN Department of Physics and Astronomy, Arizona State University, Box 871054, Tempe, AZ 85287-1504 AND DAVID S. DAVIS University of Alabama, Department of Physics and Astronomy, Tuscaloosa, AL 35487 Received 1995 September 1; accepted 1995 October 20 ABSTRACT ROSAT studies of poor groups of galaxies have revealed hot, diffuse gas only in groups dominated by E/S0 galaxies. Here we investigate the possibility that a similar, but cooler, component exists in spiral-rich groups and can be detected through absorption in QSO spectra. We find that for the expected temperature, density, and metal abundance of the intragroup medium, various high-ionization lines should be detectable. At T ~ 2 x 10^6^ K, O VI, Ne VIII, Mg x, and Si XII lines will be seen. Strong Lyman series lines are also expected. A collisionally ionized gas at these temperatures will not produce much C IV and N V absorption, since it requires a multiphase medium to produce spectra that show all of the above ions. In addition, some lines of sight will likely pass only through the intragroup gas, producing pure "high-ionization" absorption systems (i.e., O VI lines without associated C IV and N V lines). Recent Hubble Space Telescope (HST) and Keck observations have revealed the presence of absorption lines with some of the properties we predict for the intragroup medium in spiral-rich groups. The discovery of a hot intragroup medium in spiral-rich groups would have many important consequences for extragalactic astronomy, including the possible pressure confinement of low-ionization absorption-line clouds. Subject headings: cosmology: observations - galaxies: intergalactic medium - Local Group - quasars: absorption lines - ultraviolet: general
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