Astronomy and Astrophysics – Astrophysics
Scientific paper
Dec 2010
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2010dmap.conf..426r&link_type=abstract
DARK MATTER IN ASTROPHYSICS AND PARTICLE PHYSICS . Proceedings of the 7th International Heidelberg Conference on Dark 2009 . Hel
Astronomy and Astrophysics
Astrophysics
Cosmology: Theory, Cosmology: Observations, Dark Energy, Modified Gravity, X-Ray Galaxy Clusters
Scientific paper
Using two complementary X-ray galaxy cluster studies we present new constraints on dark energy and modified gravity. Using Chandra measurements of the X-ray gas mass fraction, fgas, in 42 hot, X-ray luminous, dynamically relaxed clusters spanning the redshift range 0.05 < z < 1.1, we obtain a tight constraint on the mean matter density and a detection of the effects of dark energy on the distances to the clusters comparable in significance to recent type Ia supernovae (SNIa) studies. Using measurements of the growth of cosmic structure, as inferred from the observed evolution of the X-ray luminosity function (XLF) of clusters, we obtain the first precise determination of the dark energy equation of state and constrain departures from General Relativity (GR) on cosmological scales. For the latter, we employ the growth rate parameterization, Ωm(z)γ, for which GR predicts a growth index γ 0.55. Combining the XLF with observations of the cosmic microwave background, SNIa, and fgas, to simultaneously constrain a flat cosmological constant (ΛCDM) background model, we obtain γ = 0.51{ - 0.15}{ + 0.16} , which is consistent with GR. Both the fgas and XLF analyses provide strong, independent support to the GR+ΛCDM paradigm.
Allen Steven W.
Ebeling Harald
Fabian Andrea C.
Mantz Adam
Morris Richard G.
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