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		| Paper: | Evolution of the Cluster Abundance from the ROSAT Deep Cluster Survey |  
		| Volume: | 176, Observational Cosmology: The Development of Galaxy Systems |  
		| Page: | 40 |  
		| Authors: | Borgani, Stefano; Rosati, Piero; Tozzi, Paolo; Norman, Colin |  
		| Abstract: | We use results from the Rosat Deep Cluster Survey (RDCS, Rosati et al. 1998) to characterize the evolution of the cluster abundance out to redshift z≈ 0.8. Based on the Press--Schechter approach to follow the evolution of the mass--function and on an empirical prescription to convert masses into observed X--ray cluster fluxes, we obtain constraints on cosmological models. We apply a maximum--likelihood approach to the RDCS redshift-- and luminosity--distribution. Although the resulting constraints on Ω_0 are sensitive to the assumed X--ray luminosity--temperature relation, we find that a low--density Universe with Ω_0≈ 0.3--0.5 is in general to be preferred with respect to the Ω_0 = 1 case. A critical--density Universe would require a rather strong positive evolution of the L_X--T_X relation, which seems to be in contrast with current observations. |  
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