New Constraints on Dark Energy from Chandra X-rayObservations of the Largest Relaxed Galaxy Clusters

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We present constraints on the mean matter density, {Omega}{sub m}, dark energy density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and mean baryon density, ... continued below

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19 pages

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Allen, S. W.; Rapetti, D. A.; Schmidt, R. W.; Ebeling, H.; Morris, G. & Fabian, A. C. June 6, 2007.

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We present constraints on the mean matter density, {Omega}{sub m}, dark energy density, {Omega}{sub DE}, and the dark energy equation of state parameter, w, using Chandra measurements of the X-ray gas mass fraction (fgas) in 42 hot (kT > 5keV), X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.05 < z < 1.1. Using only the fgas data for the 6 lowest redshift clusters at z < 0.15, for which dark energy has a negligible effect on the measurements, we measure {Omega}{sub m}=0.28{+-}0.06 (68% confidence, using standard priors on the Hubble Constant, H{sub 0}, and mean baryon density, {Omega}{sub b}h{sup 2}). Analyzing the data for all 42 clusters, employing only weak priors on H{sub 0} and {Omega}{sub b}h{sup 2}, we obtain a similar result on {Omega}{sub m} and detect the effects of dark energy on the distances to the clusters at {approx}99.99% confidence, with {Omega}{sub DE}=0.86{+-}0.21 for a non-flat LCDM model. The detection of dark energy is comparable in significance to recent SNIa studies and represents strong, independent evidence for cosmic acceleration. Systematic scatter remains undetected in the f{sub gas} data, despite a weighted mean statistical scatter in the distance measurements of only {approx}5%. For a flat cosmology with constant w, we measure {Omega}{sub m}=0.28{+-}0.06 and w=-1.14{+-}0.31. Combining the fgas data with independent constraints from CMB and SNIa studies removes the need for priors on {Omega}{sub b}h{sup 2} and H{sub 0} and leads to tighter constraints: {Omega}{sub m}=0.253{+-}0.021 and w=-0.98{+-}0.07 for the same constant-w model. More general analyses in which we relax the assumption of flatness and/or allow evolution in w remain consistent with the cosmological constant paradigm. Our analysis includes conservative allowances for systematic uncertainties. The small systematic scatter and tight constraints bode well for future dark energy studies using the f{sub gas} method.

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19 pages

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  • Journal Name: Monthly Notices of the Royal Astronomical Society

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  • Report No.: SLAC-PUB-12542
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 908570
  • Archival Resource Key: ark:/67531/metadc887356

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Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

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  • June 6, 2007

Added to The UNT Digital Library

  • Sept. 22, 2016, 2:13 a.m.

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  • July 26, 2017, 11:56 a.m.

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Allen, S. W.; Rapetti, D. A.; Schmidt, R. W.; Ebeling, H.; Morris, G. & Fabian, A. C. New Constraints on Dark Energy from Chandra X-rayObservations of the Largest Relaxed Galaxy Clusters, article, June 6, 2007; [Menlo Park, California]. (digital.library.unt.edu/ark:/67531/metadc887356/: accessed October 21, 2018), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.