Comparison of the Planck measured SZ flux, Y₅₀₀ and the predictions from X-ray measurements, . Cool core systems are marked as blue stars, other systems as black dots. (Left) Y_X,500 from XMM-Newton (see top-left panel of Fig. 5), and Y₅₀₀ computed at the position and θ₅₀₀ derived from XMM-Newton measurements. (Middle) Y_X,500 and Y₅₀₀ respectively from L_X,500, and position and θ₅₀₀ as given in the MCXC (Piffaretti et al. 2011). (Right) Y_X,500 from L_X,500 as given in the MCXC, while Y₅₀₀ are blind Planck measurements.