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We present updated cosmological constraints from measurements of the gas mass fractions (f₆₀ₒ) of massive, dynamically relaxed galaxy clusters. Our new data set has greater leverage on models of dark energy, thanks to the addition of the Perseus Cluster at low redshifts, two new clusters at redshifts z>0. 97, and significantly longer observations of four clusters at 0. 6<z<0. 9. Our low-redshift (z<0. 16) f₆₀ₒ data, combined with the cosmic baryon fraction measured from the cosmic microwave background (CMB), imply a Hubble constant of h = 0. 722 0. 067. Combining the full f₆₀ₒ data set with priors on the cosmic baryon density and the Hubble constant, we constrain the dark energy density to be _ = 0. 865 0. 119 in non-flat CDM (cosmological constant) models, and its equation of state to be w = -1. 13-₀. ₂₀^+0. 17 in flat, constant-w models, respectively 41 and 29 per cent tighter than our previous work, and comparable to the best constraints available from other probes. Combining f₆₀ₒ, CMB, supernova, and baryon acoustic oscillation data, we also constrain models with global curvature and evolving dark energy. For the massive, relaxed clusters employed here, we find the scaling of f₆₀ₒ with mass to be consistent with a constant, with an intrinsic scatter that corresponds to just 3 per cent in distance.
Mantz et al. (Wed,) studied this question.