X-Ray and Sunyaev-Zel'dovich Effect Measurements of the Gas Mass Fraction in Galaxy Clusters
Abstract
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 f_(gas)(X-ray) = 0.110 ± 0.003^(+0.006)_(-0.018) and f_(gas)(SZE) = 0.116 ± 0.005^(+0.009)_(-0.027) assuming (Ω_M, Ω_Λ, h) = (0.3, 0.7, 0.7); uncertainties are statistical followed by systematic at 68% confidence. For model 2, f_(gas)(X-ray) = 0.119 ± 0.003^(+0.007)_(-0.014) and f_(gas)(SZE) = 0.121 ± 0.005^(+0.009)_(-0.016). For model 3, f_(gas)(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 r_(2500) to the cosmic baryon fraction, f_(gas)/(Ω_(B)/Ω_(M)) 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 (Ω_M = 1) universe.
Additional Information
© 2006 American Astronomical Society. Received 2006 April 4; accepted 2006 July 26. We are grateful to the late Leon van Speybroeck for compiling Chandra data for a large ensemble of clusters, and to his colleagues on the Chandra project as well, especially C. Jones and H. Tananbaum, who generously shared proprietary data with us. The support of the BIMA and OVRO staff over many years is also gratefully acknowledged, including J. R. Forster, C. Giovanine, R. Lawrence, S. Padin, R. Plambeck, S. Scott, and D. Woody. We thank C. Alexander, K. Coble, A. Cooray, L. Grego, G. Holder, J. Hughes, W. Holzapfel, A. Miller, J. Mohr, S. Patel, and P. Whitehouse for their contributions to the SZE instrumentation, observations, and analysis. We thank our referee K. Romer for her helpful comments in improving the manuscript. Finally, we thank A. Kravtsov for many useful discussions. This work was supported by NASA LTSA grant NAG5-7985 and also in part by NSF grants PHY01-14422 and AST 00-96913, the David and Lucile Packard Foundation, the McDonnell Foundation, and a MSFC director's discretionary award. Research at the Owens Valley Radio Observatory and the Berkeley-Illinois-Maryland Association array was supported by NSF grants AST 99-81546 and 02-28963. S. L. and D. N. acknowledge support from the NASA Graduate Student Researchers Program. D. N. is also supported by the Sherman Fairchild Postdoctoral Fellowship at Caltech.Attached Files
Published - LARapj06.pdf
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Additional details
- Eprint ID
- 23875
- Resolver ID
- CaltechAUTHORS:20110602-110322292
- NAG5-7985
- NASA
- 01-14422
- NSF
- AST 00-96913
- NSF
- David and Lucile Packard Foundation
- McDonnell Foundation
- MSFC director's discretionary award
- NASA Graduate Student Research Fellowship
- Sherman Fairchild Foundation
- Created
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2011-06-02Created from EPrint's datestamp field
- Updated
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2021-11-09Created from EPrint's last_modified field