AAS 207th Meeting, 8-12 January 2006
Session 193 Recent Discoveries in the Far Ultraviolet
Special Session, Thursday, 10:00-11:30am, January 12, 2006, Delaware B

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[193.05] O VI Absorption Lines and the IGM Baryon Content

T. M. Tripp (University of Massachusetts)

The Far Ultraviolet Spectroscopic Explorer has observed a large number of low-redshift QSOs and AGNs, and the spectra of these objects show an array of remarkable absorption lines ranging from cold, molecular gas (e.g., traced by C I and H2) to highly ionized and hot gas (e.g., traced by O VI and Ne VIII transitions). Many of the gas clouds detected in UV absorption cannot be studied by any other technique, especially in intergalactic regions where the densities are likely to be quite low. The O VI absorption lines detected in intervening gas clouds have particularly important implications regarding the chemical enrichment, physical conditions, and baryonic content of intergalactic gas in the nearby universe. For example, these absorbers can be used to search for the "warm-hot intergalactic medium", a shock-heated phase of the IGM that is theoretically predicted to be a major baryon reservoir at the present epoch. This talk will briefly review studies of the low-z IGM based on ultraviolet observations of O VI and related absorption lines, including findings on the metallicity, ionization, and cosmological mass of these systems as well as their relationships with galaxies. While the deployment of FUSE has led to substantial progress, the observations have also raised new questions. The talk will conclude with a few comments on outstanding questions and goals for future observations.

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