95% confidence contours for the various theoretical models presented in Sect. 5.2. The results for the potential-based temperature function assuming spherical-collapse dynamics are labelled with Φ_sph, those incorporating ellipsoidal collapse with Φ_ell, respectively. While the solid curves represent the results of temperature functions that take into account merger effects, the dashed curves are for those which do not account for merging. The crosses mark the respective best-fit values. Parameter constraints from a joint analysis of WMAP5, BAO, and SN data inferred from Komatsu et al. (2009) are indicated by the black solid contour. Upper panel: Ikebe et al. (2002) data. Lower panel: Vikhlinin et al. (2009a) data.