摘要：Context.Observations of relaxed, massive, and distant clusters can provide important tests of standard cosmological models, for example by using the gas mass fraction. To perform this test, the dynamical state of the cluster and its gas properties have to be investigated. X-ray analyses provide one of the best opportunities to access this information and to determine important properties such as temperature profiles, gas mass, and the total X-ray hydrostatic mass. For the last of these, weak gravitational lensing analyses are complementary independent probes that are essential in order to test whether X-ray masses could be biased.Aims.We study the very luminous, high redshift (z= 0.902) galaxy cluster ClJ120958.9+495352 usingXMM-Newtondata. We measure global cluster properties and study the temperature profile and the cooling time to investigate the dynamical status with respect to the presence of a cool core. We useHubbleSpace Telescope (HST) weak lensing data to estimate its total mass and determine the gas mass fraction.Methods.We perform a spectral analysis using anXMM-Newtonobservation of 15 ks cleaned exposure time. As the treatment of the background is crucial, we use two different approaches to account for the background emission to verify our results. We account for point spread function effects and deproject our results to estimate the gas mass fraction of the cluster. We measure weak lensing galaxy shapes from mosaic HST imaging and select background galaxies photometrically in combination with imaging data from theWilliam HerschelTelescope.Results. The X-ray luminosity of ClJ120958.9+495352 in the 0.1–2.4 keV band estimated from ourXMM-Newtondata isLX= (13.4+1.2−1.0) × 1044erg/s and thus it is one of the most X-ray luminous clusters known at similarly high redshift. We find clear indications for the presence of a cool core from the temperature profile and the central cooling time, which is very rare at such high redshifts. Based on the weak lensing analysis, we estimate a cluster mass ofM500/1014M⊙= 4.4+2.2−2.0(stat.) + 0.6 (sys.) and a gas mass fraction offgas,2500= 0.11−0.03+0.06in good agreement with previous findings for high redshift and local clusters.
