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R. J. Williams, S. Mathur (OSU), F. Nicastro (CfA)
Cosmological hydrodynamic simulations indicate that many galaxies at low redshift reside within a tenuous reservoir of gas known as the warm-hot intergalactic medium (WHIM). We might thus expect that our own Galaxy is surrounded by the WHIM as well, and indeed, high quality far-UV and X-ray spectra of background quasars show highly ionized absorption at a redshift consistent with zero in several directions. Even so, the origin of this absorption is contentious: while it is often presumed to arise locally as a Galactic corona or fountain, there are indications that it could actually extend to megaparsec scale distances and comprise some of the local WHIM. I will present the current status of the debate as well as the latest results from our Chandra observational and archival programs. Using Chandra and FUSE spectral line measurements coupled with curve-of-growth and ionization balance models, we show that the local absorption is indeed consistent with the WHIM. Furthermore, even though a Galactic origin cannot be definitively ruled out, the observed X-ray absorption is not likely to coexist with any known lower-ionization Galactic component.
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Bulletin of the American Astronomical Society, 37 #4
© 2005. The American Astronomical Soceity.