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2006ApJ...652..917L - Astrophys. J., 652, 917-936 (2006/December-1)

X-ray and Sunyaev-Zel'dovich effect measurements of the gas mass fraction in galaxy clusters.


Abstract (from CDS):

We present gas mass fractions of 38 massive galaxy clusters at redshifts 0.14≤z≤0.89, derived from Chandra X-ray and OVRO/BIMA interferometric Sunyaev-Zel'dovich effect (SZE) measurements. We use three models for the gas distribution: (1) an isothermal β-model fit jointly to the X-ray data at radii beyond 100 kpc and to all of the SZE data, (2) a nonisothermal double β-model in hydrostatic equilibrium with a Navarro-Frenk-White (NFW) dark matter distribution, fit jointly to all of the X-ray and SZE data, and (3) an isothermal β-model fit only to the SZE spatial data. We show that the isothermal model well characterizes the intracluster medium outside the cluster core and provides good fits to clusters with a range of morphological properties. X-ray and SZE mean gas mass fractions for model 1 are fgas(X-ray)=0.110±0.003+0.006–0.018 and fgas(SZE)=0.116±0.005+0.009–0.026assuming ΩMΛ,h=0.3,0.7,0.7; uncertainties are statistical followed by systematic at 68% confidence. For model 2, fgas(X-ray)=0.119±0.003+0.007–0.014and fgas(SZE)=0.121±0.005+0.009–0.016. For model 3, fgas(SZE)=0.120±0.009+0.009–0.027. The agreement in the results shows that the core can be accounted for satisfactorily by either excluding it from fits to the X-ray data or modeling the intracluster gas with a nonisothermal double β-model. We find that the SZE is largely insensitive to core structure. Our results indicate that the ratio of gas mass fraction within r2500to the cosmic baryon fraction, fgasBM, is 0.68+0.10–0.16, where statistical and systematic uncertainties are included at 68% confidence. By assuming that cluster gas mass fractions are independent of redshift, we find that the results agree with standard ΛCDM cosmology and are inconsistent with a flat matter-dominated (ΩM=1) universe.

Abstract Copyright:

Journal keyword(s): Cosmology: Cosmological Parameters - Cosmology: Observations - X-Rays: Galaxies: Clusters

Simbad objects: 42

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