X-ray unabsorbed flux versus SZ flux. For Planck SZ detections identified with MCXC clusters (open green circles), the X-ray flux is estimated from L₅₀₀. For other Planck SZ detections, the flux is derived from RASS count-rate in a five-arcmin aperture (see Sect. 4.1.1). Planck new clusters and class1 candidates are shown as open red circles and squares, respectively. The two lines corresponds to the expected L₅₀₀–Y₅₀₀ relation (Arnaud et al. 2010) at z = 0.01 and z = 1, respectively.