August 21, 2002
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May 1, 2002
We present precise measurements of the X-ray gas mass fraction for a sample of luminous, relatively relaxed clusters of galaxies observed with the Chandra Observatory, for which independent confirmation of the mass results is available from gravitational lensing studies. Parameterizing the total (luminous plus dark matter) mass profiles using the model of Navarro, Frenk & White (1997), we show that the X-ray gas mass fractions in the clusters asymptote towards an approximatel...
August 13, 2002
For the first time the large-scale clustering and the mean abundance of galaxy clusters are analysed simultaneously to get precise constraints on the normalized cosmic matter density $\Omega_m$ and the linear theory RMS fluctuations in mass $\sigma_8$. A self-consistent likelihood analysis is described which combines, in a natural and optimal manner, a battery of sensitive cosmological tests where observational data are represented by the (Karhunen-Lo\'{e}ve) eigenvectors of ...
November 10, 2009
This is the third of a series of papers in which we derive simultaneous constraints on cosmological parameters and X-ray scaling relations using observations of the growth of massive, X-ray flux-selected galaxy clusters. Our data set consists of 238 clusters drawn from the ROSAT All-Sky Survey, and incorporates extensive follow-up observations using the Chandra X-ray Observatory. Here we present improved constraints on departures from General Relativity (GR) on cosmological s...
March 8, 1999
In this letter, we present a new determination of the local (z<0.09) X-ray luminosity function (XLF) using a large, statistical sample of 294 Abell clusters and the ROSAT All-Sky-Survey. Given our large sample size, we have reduced errors by a factor of two for L(X)(0.5-2keV)>10^43 ergs/sec. We combine our data with previous work in order to explore possible constraints imposed by the shape of the XLF on cosmological models. A set of currently viable cosmologies is used to co...
April 17, 2009
(Abriged) We present the analysis of the baryonic content of 52 X-ray luminous galaxy clusters observed with Chandra in the redshift range 0.3-1.273. We use the deprojected X-ray surface brightness profiles and the measured values of the gas temperature to recover the gas and total mass profiles. By assuming that galaxy clusters are representative of the cosmic baryon budget, the distribution of the cluster baryon fraction in the hottest (T> 4 keV) systems as a function of re...
December 15, 2008
Chandra observations of large samples of galaxy clusters detected in X-rays by ROSAT provide a new, robust determination of the cluster mass functions at low and high redshifts. Statistical and systematic errors are now sufficiently small, and the redshift leverage sufficiently large for the mass function evolution to be used as a useful growth of structure based dark energy probe. In this paper, we present cosmological parameter constraints obtained from Chandra observations...
January 4, 1999
The ROSAT Deep Cluster Survey (RDCS) has provided a new large deep sample of X-ray selected galaxy clusters. Observables such as the flux number counts n(S), the redshift distribution n(z) and the X-ray luminosity function (XLF) over a large redshift baseline (z\lesssim 0.8) are used here in order to constrain cosmological models. Our analysis is based on the Press-Schechter approach, whose reliability is tested against N-body simulations. Following a phenomenological approac...
December 11, 2001
We summarize some of the major results obtained so far from the REFLEX survey of X-ray clusters of galaxies, concentrating on the latest measurements of the cluster X-ray luminosity function and two-point correlation function. The REFLEX luminosity function provides the most homogeneous census of the distribution function of masses in the local Universe, representing a unique zero-redshift reference quantity for evolutionary studies. On the other hand, the observed clustering...
May 18, 2004
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 c...
October 25, 2002
Different determinations currently suggest scattered values for the power spectrum normalization on the scale of galaxy clusters, sigma_8. Here we concentrate on the constraints coming from the X-ray temperature and luminosity functions (XTF and XLF), and investigate several possible sources of discrepancies in the results. We conclude that the main source of error in both methods is the scaling relation involved, in particular the way its intrinsic scatter and systematic nor...