Temperature bias in measurements of the Hubble constant using the Sunyaev - Zeldovich effect

Mar, 2003
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200320042005021
Abstract: (arXiv)
Measurements of the Hubble constant to distant galaxy clusters using the Sunyaev-Zeldovich effect are systematically low in comparison to values obtained by other means. These measurements usually assume a spherical isothermal β\beta model for the intracluster medium (ICM). We present the results of a statistical analysis of {\em temperature bias} in H0H_0 determinations in a sample of 27 numerically simulated X-ray clusters drawn from a Λ\LambdaCDM model at z=0.5. We employ adaptive mesh refinement to provide high resolution (15.6 h1kpc^{-1} kpc) in cluster cores which dominate the X-ray and radio signals. Fitting synthetic X-ray and y-parameter maps to the standard isothermal beta model, we find a broad, skewed distribution in fH0(SZ)/H0(actual)f\equiv H_0(SZ)/H_0(actual) with a mean, median, and standard deviation of 0.89, 0.83 and 0.32 respectively, where H0(SZ)H_0(SZ) is the value of H0H_0 derived by using Sunyaev-Zeldovich effect method and H0(actual)H_0(actual) is the value used in the cosmological simulation. We find that the clusters' declining temperature profiles systematically lower estimates of H0H_0 by 10% to 20%. The declining temperature profile of our adiabatic system is consistent with the result including radiative cooling and supernovae feedback (Loken et al. 2002). We thereby introduce a non-isothermal β\beta model as an improvement. Applying the non-isothermal β\beta model to the refined sample with well-fitted temperature profile, the value of f improves 9% relative to the actual value. The study of the morphology and the clumping effects conclude that these two factors combine to induce scatter in f of ±\pm 30 %.
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