IAU02232
Presentation type requested: ORAL
CHANDRA AND FUSE VIEW OF THE WHIM:THE LOCAL GROUP AND BEYOND
Fabrizio Nicastro
Smithsonian Astrophysical Observatory
In this contribution I will present and discuss evidence for the existence of a diffuse and warm medium pervading our own Local Group. This evidence is based on the detection of absorption lines from highly ionized metals in the UV and X-ray bands along all the lines for which high resolution X-ray spectra with enough statistics are available, and on the kinematics of the HV-OVI absorbers. This medium has a baryonic mass that can be as large as 2e12 solar masses, enough to synamically stabilize the Local Group. The [Ne/O] measured ratio is largely over-solar, suggesting that depletion plays an important role and providing clues on the sources responsible for metal-feeding the IGM. I will also present preliminary results from our recent Chandra TOO of Mkn 421. During the observation the source was at a flux level > 0.1 Crab: by far the brightest AGN in the sky. With these data we can probe for the first time the existence of an intervening "X-ray Forest" of absorption lines from highly ionized intergalactic gas outside our own Local Group. This previously unseen baryonic component contains the majority of the matter in the local Universe.
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