HIGH-IONIZATION QUASAR ABSORPTION-LINES - A TEST OF THE EXISTENCE OF HOT GAS IN SPIRAL-RICH GROUPS

ROSAT studies of poor groups of galaxies have revealed hot, diffuse ga s only in groups dominated by E/SO galaxies. Here we investigate the p ossibility 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 th e intragroup medium, various high-ionization lines should be detectabl e. At T similar to 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 collision ally ionized gas at these temperatures will not produce much C IV and N V absorption, since it requires a multiphase medium to produce spect ra that show all of the above ions. In addition, some lines of sight w ill 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 obse rvations have revealed the presence of absorption lines with some of t he properties we predict for the intragroup medium in spiral-rich grou ps. The discovery of a hot intragroup medium in spiral-rich groups wou ld have many important consequences for extragalactic astronomy, inclu ding the possible pressure confinement of low-ionization absorption-li ne clouds.