Ω₀ from the Apparent Evolution of Gas Fractions in Rich Clusters of Galaxies
Danos, Rebecca · Pen, Ue-Li
Original · EN
We apply a unique gas fraction estimator to published X-ray cluster properties and we compare the derived gas fractions of observed clusters to simulated ones. The observations are consistent with a universal gas fraction of 0.15+/-0.01h₅₀⁻³/² for the low redshift clusters that meet our selection criteria. The fair sampling hypothesis states that all clusters should have a universal constant gas fraction for all times. Consequently, any apparent evolution would most likely be explained by an incorrect assumption for the angular-diameter distance relation. We show that the high redshift cluster data is consistent with this hypothesis for Ω₀<0.63 (95% formal confidence, flat Λ model) or Ω₀<0.60 (95% formal confidence, hyperbolic open model). The maximum likelihood occurs at Ω₀=0.2 for a spatially flat cosmological constant model.
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