X-Ray and Sunyaev-Zel’dovich Effect Measurements of the Gas Mass Fraction in Galaxy Clusters

By S. LaRoque, M. Bonamente, J. Carlstrom, M. Joy, D. Nagai, E. Reese, K. Dawson. 2006

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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 and fgas(SZE) = 0.116 ± 0.005 assuming = ; uncertainties are statistical followed by systematic at 68% confidence. For model 2, fgas(X-ray) = 0.119 ± 0.003 and fgas(SZE) = 0.121 ± 0.005. For model 3, fgas(SZE) = 0.120 ± 0.009. 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 r2500 to the cosmic baryon fraction, fgas/ , is 0.68, 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.

Subfields: Astronomy and Astrophysics, Instrumentation

View Paper: https://www.semanticscholar.org/paper/757797f4073fdf3475b697f3d48115db0a7d1d76

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Citations in the corpus

Hydrodynamical N-body simulations of coupled dark energy cosmologies (2008, background): “This could in fact alleviate tensions between the high baryon abundance estimated from CMB observations, and the somewhat lower values inferred from detailed X-ray observations of galaxy clusters (Vikhlinin et al. 2006; LaRoque et al. 2006; Afshordi et al. 2007; McCarthy, Bower & Balogh 2007).”
X-ray–optical classification of cluster mergers and the evolution of the cluster merger fraction (2011, methodology): “The system was also successfully targeted in Sunyaev–Zel’dovich observations (LaRoque et al. 2006).”
Formation of Galaxy Clusters (2012, background): “…to constrain cosmological parameters, as in the case of X–ray measurements of gas fractions in clusters (Allen et al. 2008, 2004; Ettori et al. 2009; Ettori, Tozzi & Rosati 2003; LaRoque et al. 2006) or abundance evolution ofclusters as a function of their observable (e.g., Vikhlinin et al. 2009c).”
Evidence for non-hydrostatic gas from the cluster X-ray to lensing mass ratio (2007, result): “We find that our masses on the average in excellent agreement with the two samples, with the LaRoque et al. (2006) values being somewhat lower, and the Allen et al. (2007) values somewhat higher, than ours.”
Virial Scaling of Massive Dark Matter Halos: Why Clusters Prefer a High Normalization Cosmology (2007, background): “…scatter in these relations is a few tens of percent or less (O’Hara et al. 2006), making these signatures, and derived quantities such as the gas mass fraction (Allen et al. 2004; LaRoque et al. 2006), a foundation for likelihood estimates of cosmological parameters (Voit 2005; Lima & Hu 2005).”
Cosmological Parameters from Observations of Galaxy Clusters (2011, result): “Within r2500 (r <∼ 0.3r200), the observed fgas profile is consistent with previous Chandra and SZ measurements for other massive, relaxed clusters (Allen et al. 2004, 2008; LaRoque et al. 2006).”
Improved constraints on dark energy from Chandra X-ray observations of the largest relaxed galaxy clusters (2007, methodology): “…is neither expected nor observed in studies where a restriction to morphologically relaxed clusters is not employed e.g. compare the small scatter measured here with the much larger scatter observed in the studies of LaRoque et al. (2006) and Ettori et al. (2003); see also Nagai et al. (2007a).”
Cosmology and astrophysics from relaxed galaxy clusters - II. Cosmological constraints (2014, methodology): “Allen et al. (2004) provided the first detection of the acceleration of the cosmic expansion from fgas data, and more recently expanded and improved their analysis (Allen et al. 2008, hereafter A08; see also LaRoque et al. 2006; Ettori et al. 2009).”
CHANDRA CLUSTER COSMOLOGY PROJECT. II. SAMPLES AND X-RAY DATA REDUCTION (2008, background): “…more complicated because the observed gas fraction in clusters is significantly lower than the cosmic average (e.g., Ettori 2003; Allen et al. 2004; LaRoque et al. 2006; Afshordi et al. 2007) and, moreover, there are trends of observed fg with the cluster mass (e.g., Mohr et al.; 1999, V06; Zhang…”