Constraining omega from X-ray properties of clusters of galaxies at high redshifts

Properties of high redshift clusters are a fundamental source of information for cosmology. It has been shown by Oukbir and Blanchard (1997) that the combined knowledge of the redshift distribution of X-ray clusters of galaxies and the luminosity-temperature correlation, L-X - T-X, provides a powerful test of the mean density of the Universe. In this paper, we address the question of the possible evolution of this relation from an observational point of view and its cosmological significance. We introduce a new indicator in order to measure the evolution of the X-ray luminosity-temperature relation with redshift and take advantage of the recent availability of temperature information for a significant number of high and intermediate redshift X-ray clusters of galaxies. From our analysis, we find a slightly positive evolution in the L-X - T-X relation. This implies a high value of the density parameter of 0.85 +/- 0.2. However, because the selection of clusters included in our sample is unknown, this can be considered only as a tentative result. A well-controlled X-ray selected survey would provide a more robust answer. XMM will be ideal for such a program.