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OATS-DAUT SEMINAR
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Speaker: Tae-Sun Kim (INAF-OATS)
Title: Missing baryons at z ~ 0: the latest view from 14 QSO spectra with the Cosmic Origins Spectrograph onboard HST
Date: Wednesday, January 15th, 2014
Time: 11:30
Venue: Villa Bazzoni
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Abstract At low redshift, detectable baryons from the diffuse, cool intergalactic medium, galaxies and the hot intracluster
medium add up only ~50% of the predicted baryons. This has led to a hypothesis of existence of the Warm-Hot
Intergalactic Medium (WHIM) with the temperature of log T = 5-7, which makes up the rest of the low-z baryons.
The detection of the hot regime of the WHIM requires X-ray observations of O VII and/or O VIII. However, most
of the claimed X-ray detections of O VII/O VIII beyond z = 0 are highly controversial. The detection of the warm
regime of the WHIM has been much more reliable and successful through UV O VI/Ne VIII along with weak, very
broad Ly-alpha absorbers in the distant QSO spectra. In addition, understanding the origin of the ionization mechanism
of O VI/Ne VIII gas is crucial for determining elemental abundances in the gas and for ultimately understanding the
total baryonic content. I present the results of the latest low-z intergalactic O VI absorber survey based on 14 high
signal-to-noise QSO spectra taken with the Cosmic Origins Spectrograph onboard HST.
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Contact: Matteo Viel (OATS)