Constraining our Universe with X‐ray and optical cluster data

We have used recent X‐ray and optical data in order to impose some constraints on the cosmology and cluster scaling relations. Generically, two kinds of hypotheses define our model. First, we consider that the cluster population is well described by the standard Press–Schechter (PS) formalism, and secondly, these clusters are assumed to follow scaling relations with mass: temperature–mass (T–M) and X‐ray luminosity–mass (L x –M) . In contrast with many other authors we do not assume specific scaling relations to model cluster properties such as the usual T–M virial relation or an observational relation or an observational determination of the L x –T relation. Instead we consider general unconstrained parameter scaling relations. With the previous model (PS plus scalings) we fit our free parameters to several X‐ray and optical data sets with the advantage over preceding works that we consider all the data sets at the same time. This prevents us from being inconsistent with some of the available observations. Among other interesting conclusions, we find that only low‐density universes are compatible with all the data considered and that the degeneracy between Ω m and σ 8 is broken. Also we obtain interesting limits on the parameters characterizing the scaling relations.