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Paper: Hot Gas in Galaxy Groups: Impact on Galaxy Evolution
Volume: 329, Nearby Large-Scale Structures and the Zone of Avoidance
Page: 77
Authors: Burstein, D.
Abstract: Over the past 15 years we have learned that most galaxies are in galaxy groups, rather than in galaxy clusters. Galaxy groups are of two types: those with gE and/or S0 galaxies in them, and those without gE and/or S0 galaxies. "E-rich" galaxy groups have twice the velocity dispersion, 2.5 times the M/L, and many more galaxies than do "S-rich" groups. Galaxy groups are real, bound systems. Hot, X-ray emitting gas is known to exist in E-rich groups. If such hot gas exists in S-rich groups (Galactic HI obscures the X-ray emission from our view), it can cool well within a Hubble time. The existence of HI "high-velocity-clouds" around the Milky Way, M31 and other nearby spirals (out to 50 kpc distance from M31) is consistent with the idea that hot gas is cooling in these galaxy groups. Similarly, the existence of spirals near lines-of-sight that yield high ionization absorption lines in bright quasar spectra. If hot X-ray emitting gas exists in spiral-rich groups, one can expect that it will have many consequences for the evolution of the galaxies in these types of groups (which include the Local Group), many of which are discussed in Burstein & Blumenthal, and some of which are explored in this paper.
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