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Date and Time of the Query: 2018-11-17 T09:22:25 PST
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For refcode 1994ApJ...421L..63H:
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1994ApJ...421L..63H THE BARYONIC FRACTION IN GROUPS OF GALAXIES FROM X-RAY MEASUREMENTS MARK J. HENRIKSEN AND GARY A. MAMON Received 1993 September 14; accepted 1993 November 12 ABSTRACT The recent ROSAT X-ray detections of hot intergalactic gas in three groups of galaxies are reviewed, and the resulting baryonic fraction in these groups is reevaluated. We show that the baryonic fraction obtained, assuming hydrostatic equilibrium, should depend, perhaps sensitively, on the radius out to which the X-rays are detected, and the temperature profile of the gas. We find that the NGC 2300 group has a baryonic fraction out to 25' of at least 20%, thus over 5 times higher than in the original analysis of Mulchaey et al. and also much higher than one would obtain from big bang nucleosynthesis, but similar to the other two groups as well as rich clusters. With this baryonic fraction, groups would be fair tracers of the distribution of baryons in the universe if {OMEGA}h_50_^2^ = 0.3. A baryonic fraction that increases with radius is consistent with the X-ray data from all three groups. However, a detailed analysis of the NGC 2300 group shows that the dependence of baryonic fraction on radius is not well constrained by the data, in part because of uncertainties in the estimated background. Subject headings: cosmology: observations - dark matter - galaxies: intergalactic medium
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