BeppoSAX observations of three distant, highly luminous clusters of galaxies:: RXJ1347-1145, Zwicky 3146 and Abell 2390

We present an analysis of BeppoSAX observations of three clusters of galaxies that are amongst the most luminous in the Universe: RXJ1347-1145, Zwicky 3146 and Abell 2390. Using data from both the Low Energy (LECS) and Medium Energy (MECS) Concentrator Spectrometers, and a joint analysis with the Phoswich Detection System (PDS) data above 10 keV, we constrain, with a relative uncertainty of between 7 and 42 per cent (90 per cent confidence level), the mean gas temperature in the three clusters. These measurements are checked against any possible non-thermal contribution to the plasma emission and are shown to be robust. We confirm that RXJ1347-1145 has a gas temperature that lies in the range between 13.2 and 22.3 keV at the 90 per cent confidence level, and is larger than 12.1 keV at 3 sigma level. The existence of such a hot galaxy cluster at redshift of about 0.45 implies an upper limit on the mean mass density in the Universe, Omega (m), of 0.5. Combining the BeppoSAX estimates for gas temperature and luminosity of the three clusters presented in this work with ASCA measurements available in the literature, we obtain a slope of 2.7 in the L-T relation once the physical properties are corrected from the contamination from the central cooling flows.