BeppoSAX observations of two high redshift clusters of galaxies: RXJ 0152.7-1357 and MS 2053.7-0449

We present X-ray observations of two high redshift clusters of galaxies car ried out with the BeppoSAX satellite. One cluster, RXJ0152.7-1357 at z simi lar or equal to 0.83, was selected from the ROSAT Deep Cluster Survey sampl e, as one of the most X-ray luminous systems known at z > 0.5. The optical and ROSAT-PSPC data show a complex morphology with at least two cores. Our SAX observations yield a gas temperature kT = 6.46(-1.19)(+1.74) keV and a metallicity A = 0.53(-0.24)(+0.29), with a prominent iron K-alpha line. The second cluster, MS 2053.7-0449 at z similar or equal to 0.58, was selected from the EMSS sample. Given the poor statistics no constraints on the meta llicity can be derived fi om the present data. Large uncertainties are asso ciated to the gas temperature (kT = 6.7(-2.3)(+6.8) keV), which has been ob tained after fixing the abundance to 0.3 solar. Combining these results wit h those obtained for similarly high redshift (z = 0.5) clusters of galaxies with broad band X-ray spectra, we discuss the high redshift L-bol - T rela tionship. The data can easily be accommodated with a non-evolving (or mildl y evolving) L-bol - T relation, a result which, when combined with the litt le observed evolution in the bulk of the X-ray cluster population, gives su pport to low Omega cosmological models.