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Measuring $Ω_m$ with the ROSAT Deep Cluster Survey

S. Borgani·P. Rosati·P. Tozzi·S. A. Stanford·P. E. Eisenhardt·C. Lidman·B. Holden·R. Della Ceca·C. Norman·G. Squires
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Abstract

We analyze the ROSAT Deep Cluster Survey (RDCS) to derive cosmological constraints from the evolution of the cluster X-ray luminosity distribution. The sample contains 103 galaxy clusters out to z=0.85 and flux-limit Flim=3 10^{-14} cgs (RDCS-3) in the [0.5-2.0] keV energy band, with a high-z extension containing four clusters at 0.90 1 10^{-14} cgs (RDCS-1). Model predictions for the cluster mass function are converted into the X-ray luminosity function in two steps. First we convert mass into intra-cluster gas temperature by assuming hydrostatic equilibrium. Then temperature is converted into X-ray luminosity by using the most recent data on the Lx-T relation for nearby and distant clusters. These include the Chandra data for seven distant clusters at 0.57<z<1.27. From RDCS-3 we find Ω_m=0.35+/-0.12 and σ_8=0.66+/-0.06 for a spatially flat Universe with cosmological constant, with no significant constraint on Γ. Even accounting for theoretical and observational uncertainties in the mass/X-ray luminosity conversion, an Einstein-de-Sitter model is always excluded at far more than the 3sigma level.

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S. Borgani, P. Rosati, P. Tozzi, S. A. Stanford, P. E. Eisenhardt, C. Lidman, B. Holden, R. Della Ceca, C. Norman, G. Squires. 2001-06-24. Measuring $Ω_m$ with the ROSAT Deep Cluster Survey. https://doi.org/10.1086/323214

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