For refcode 2009A&A...501...61E: Retrieve 59 NED objects in this reference. Please click here for ADS abstract
NED Abstract
Copyright by European Southern Observatory (ESO).
Reproduced by permission
2009A&A...501...61E
The cluster gas mass fraction as a cosmological probe: a revised study
Ettori, S.; Morandi, A.; Tozzi, P.; Balestra, I.; Borgani, S.; Rosati, P.;
Lovisari, L.; Terenziani, F.
Abstract. Context: We present the analysis of the baryonic content of 52
Xray luminous galaxy clusters observed with Chandra in the redshift range
0.31.273. Aims: Our study aims at resolving the gas mass fraction in
these objects to place constraints on the cosmological parameters
{OMEGA}_m, {OMEGA}_{LAMBDA}_ and the ratio between the pressure and
density of the dark energy, w. Methods: We deproject the Xray surface
brightness profiles to recover the gas mass profiles and fit a single
thermal component to the spectrum extracted from a region around the
cluster that maximizes the signaltonoise ratios in the observation. The
measured values of the gas temperature are used to evaluate the
temperature profile with a given functional form and to estimate the total
gravitating mass in combination with the gas density profiles. These
measured quantities are then used to statistically estimate the gas
fraction and the fraction of mass in stars. By assuming that galaxy
clusters are representative of the cosmic baryon budget, the distribution
of the cluster baryon fraction in the hottest (T_gas > 4 keV) systems as a
function of redshift is used to constrain the cosmological parameters. We
discuss how our constraints are affected by several systematic effects,
namely the isothermality, the assumed baryon fraction in stars, the
depletion parameter and the sample selection. Results: By using only the
cluster baryon fraction as a proxy for the cosmological parameters, we
obtain that {OMEGA}_m_ is very well constrained at the value of 0.35 with
a relative statistical uncertainty of 11% (1{sigma} level; w=1) and a
further systematic error of about (6,+7)%. On the other hand, constraints
on {OMEGA}_{LAMBDA}_ (without the prior of flat geometry) and w (using the
prior of flat geometry) are definitely weaker due to the presence of
greater statistical and systematic uncertainties (of the order of 40 per
cent on {OMEGA}_{LAMBDA}_ and greater than 50 per cent on w). If the WMAP
5year bestfit results are assumed to fix the cosmological parameters, we
limit the contributions expected from nonthermal pressure support and ICM
clumpiness to be lower than about 10 per cent, also leaving room to
accommodate baryons not accounted for either in the Xray emitting plasma
or in stars of the order of 18 per cent of the total cluster baryon
budget. This value is lowered to zero for a noflat Universe with
{OMEGA}_{LAMBDA}_>0.7.
Key words: galaxies: clusters: general, galaxies: fundamental parameters,
intergalactic medium, Xrays: galaxies: clusters, cosmology: observations,
dark matter
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