TY  - JOUR
A1  - Sanders, J. S.
A1  - Fabian, A. C.
A1  - Allen, S. W.
A1  - Schrnidt, R. W.
T1  - Mapping small-scale temperature and abundance structures in the core of the Perseus cluster
N2  - We report further results from a 191-ks Chandra observation of the core of the Perseus cluster, Abell 426. The emission-weighted temperature and abundance structures are mapped in detail. There are temperature variations down to similar to1 kpc in the brightest regions. Globally, the strongest X-ray surface brightness features appear to be caused by temperature changes. Density and temperature changes conspire to give approximate azimuthal balance in pressure showing that the gas is in hydrostatic equilibrium. Si, S, Ar, Ca, Fe and Ni abundance profiles rise inwards from abo
Y1  - 2004
SN  - 0035-8711
ER  - 
TY  - JOUR
A1  - Allen, S. W.
A1  - Schmidt, Robert W.
A1  - Ebeling, H.
A1  - Fabian, A. C.
A1  - van Speybroeck, L.
T1  - Constraints on dark energy from Chandra observations of the largest relaxed galaxy clusters
N2  - We present constraints on the mean dark energy density, Omega(X) and dark energy equation of state parameter, w(X), based on Chandra measurements of the X-ray gas mass fraction in 26 X-ray luminous, dynamically relaxed galaxy clusters spanning the redshift range 0.07 < z < 0.9. Under the assumption that the X-ray gas mass fraction measured within r(2500) is constant with redshift and using only weak priors on the Hubble constant and mean baryon density of the Universe, we obtain a clear detection of the effects of dark energy on the distances to the clusters, confirming (at comparable significance) previous results from Type la supernovae studies. For a standard Lambda cold dark matter (CDM) cosmology with the curvature Omega(K) included as a free parameter, we find Omega(Lambda) = 0.94(-0.23)(+0.21) (68 per cent confidence limits). We also examine extended XCDM dark energy models. Combining the Chandra data with independent constraints from cosmic microwave background experiments, we find Omega(X) = 0.75 +/- 0.04, Omega(m) = 0.26(- 0.04)(+0.06) and w(X) =-1.26 +/- 0.24. Imposing the prior constraint w(X) > -1, the same data require w(X) < -0.7 at 95 per cent confidence. Similar results on the mean matter density and dark energy equation of state parameter, &UOmega;(m) = 0.24 ± 0.04 and w(X) 1.20(-0.28)(+0.24), are obtained by replacing the cosmic microwave background data with standard priors on the Hubble constant and mean baryon density and assuming a flat geometry
Y1  - 2004
SN  - 0035-8711
ER  - 
TY  - JOUR
A1  - Schmidt, Robert W.
A1  - Allen, S. W.
A1  - Fabian, A. C.
T1  - An improved approach to measuring H-0 using X-ray and SZ observations of galaxy clusters
N2  - We present an improved method for predicting the Sunyaev-Zeldovich (SZ) effect in galaxy clusters from spatially resolved, spectroscopic X-ray data. Using the deprojected electron density and temperature profiles measured within a fraction of the virial radius, and assuming a Navarro-Frenk-White mass model, we show how the pressure profile of the X-ray gas can be extrapolated to large radii, allowing the Comptonization parameter profile for the cluster to be predicted precisely. We apply our method to Chandra observations of three X-ray-luminous, dynamically relaxed clusters with published SZ data: RX J1347.5-1145, Abell 1835 and Abell 478. Combining the predicted and observed SZ signals, we determine improved estimates for the Hubble constant from each cluster and obtain a weighted mean of H (0) = 69 +/- 8 km s(-1) Mpc(-1) for a cosmology with Omega(m) = 0.3 and Omega(Lambda) = 0.7. This result is in good agreement with independent findings from the Hubble Key Project and the combination of cosmic microwave background and galaxy cluster data
Y1  - 2004
SN  - 0035-8711
ER  -