Mon. Not. R. Astron. Soc., 353, 457-467 (2004/September-2)
Constraints on dark energy from Chandra observations of the largest relaxed galaxy clusters.
ALLEN S.W., SCHMIDT R.W., EBELING H., FABIAN A.C. and VAN SPEYBROECK L.
Abstract (from CDS):
We present constraints on the mean dark energy density, ΩX and dark energy equation of state parameter, wX, based on Chandra measurements of the X-ray gas mass fraction in 26 X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.07 < z < 0.9. Under the assumption that the X-ray gas mass fraction measured within r2500is constant with redshift and using only weak priors on the Hubble constant and mean baryon density of the Universe, we obtain a clear detection of the effects of dark energy on the distances to the clusters, confirming (at comparable significance) previous results from Type Ia supernovae studies. For a standard Λ cold dark matter (CDM) cosmology with the curvature ΩKincluded as a free parameter, we find ΩΛ= 0.94+0.21–0.23 (68 per cent confidence limits). We also examine extended XCDM dark energy models. Combining the Chandra data with independent constraints from cosmic microwave background experiments, we find ΩX= 0.75±0.04, Ωm= 0.26+0.06–0.04and wX=-1.26±0.24. Imposing the prior constraint wX> -1, the same data require wX< -0.7 at 95 per cent confidence. Similar results on the mean matter density and dark energy equation of state parameter, Ωm= 0.24±0.04 and wX=-1.20+0.24–0.28, are obtained by replacing the cosmic microwave background data with standard priors on the Hubble constant and mean baryon density and assuming a flat geometry.
gravitational lensing - cosmic microwave background - cosmological parameters - dark matter - X-rays: galaxies: clusters
Tables 1, 2: 4C 55= 4C 55.16, cluster = NAME 4C 55 CLUSTER.
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