Cosmological Constraints from theROSATDeep Cluster Survey

The ROSAT Deep Cluster Survey (RDCS) has provided a new large deep sample of X-ray selected galaxy clusters. Observables such as the flux number counts n ( S ), the redshift distribution n ( z ), and the X-ray luminosity function (XLF) over a large redshift baseline ( z ≲0.8) are used here in order to constrain cosmological models. Our analysis is based on the Press-Schechter approach, whose reliability is tested against N -body simulations. Following a phenomenological approach, no assumption is made a priori on the relation between cluster masses and observed X-ray luminosities. As a first step, we use the local XLF from RDCS, along with the high-luminosity extension provided by the XLF from the Brightest Cluster Survey, in order to constrain the amplitude of the power spectrum, σ 8 , and the shape of the local luminosity-temperature, L bol - T , relation. We obtain σ 8 =(0.58 ± 0.06) × Ω 0 -0.47+0.16Ω for flat models (Ω Λ =1-Ω 0 ) and σ 8 =(0.58 ± 0.06) × Ω 0 -0.53+0.27Ω for open models (Ω Λ =0) at a 90% confidence level, almost independent of the L bol - T shape. The density parameter Ω 0 and the evolution of the L bol - T relation are constrained by the RDCS XLF at z >0 and the EMSS XLF at =0.33, and by the RDCS n ( S ) and n ( z ) distributions. By modeling the evolution for the amplitude of the L bol - T relation as (1+ z ) A , an Ω 0 =1 model can be accommodated for the evolution of the XLF with 1≲ A ≲3 at a 90% confidence level, while Ω 0 =0.4 +0.3 −0.2 and Ω 0 ≲0.6 are implied by a nonevolving L bol - T ( A =0) for open and flat models, respectively.