High Redshift X-Ray Clusters and Ω₀

Abstract

Clusters of galaxies axe undoubtedly the largest virialized systems in the universe, they offer a powerful tool in constraining cosmological parameters. For example, their present-day abundance has been used to constrain parameters such as the shape n and the amplitude σ8 of the mass fluctuations as well the cosmological density parameter Ω0 However this constraint is degenerate in σ8 and Ω0 ₀ Recently, Oukbir & Blanchard (1997; hereafter OB97), have nicely shown that the evolution of X-ray temperature distribution function does depend strongly on Ω0, and claimed that the combined knowledge of the abundance of X-ray clusters together with the evolution of the luminosity-temperature relation would allow us to strongly constrain the cosmological density parameter independently of the power spectrum. I will present the result of our first attempt to apply this test to current X-ray data (Sadat et al. 1997).