Unveiling the most massive clusters at z>0.5 with Planck and XMM-Newton.

We propose to gather spatially resolved spectroscopy of a sample of 33 massive(M_{500}>5e+14 solar masses) clusters detected blindly by Planck and confirmedtoday to be in the redshift range 0.5<z<1. Using for the first time astatistically significant sample in this highmass, highredshift regime, wewill study the fundamental scalings between Y_SZ, Y_X and M_500, and thepressure and entropy profiles. This will provide an important probe of thephysics of cluster gravitational collapse and be of large legacy value for thecosmological exploitation of the Planck sample. Complementary VLT observationsare proposed. This proposal is submitted on behalf of the Planck collaboration. truncated!, Please see actual data for full text [truncated!, Please see actual data for full text]