(black points). The phenomenon is present in the entire mass range but it is less pronounced for the three most massive systems at $z=2$ that, indeed, lie extremely close to the black solid line representing the $z=0$ scaling relation. These 3 objects have recently experienced a major merger. As consequence, their mass is doubled (notice the mass separation from the rest of the sample), and their gas has been strongly heated by the induced shocks. To secure that our result was not influenced by the limited number of objects, we verified which fraction, among the highest mass systems in the $z \sim 2.3 $ MUSIC sample[^6] [@sembolini.etal.2013; @sembolini.etal.2014], has recently experienced a major merger. We found that this condition is verified for 10 systems out of the 11 objects with mass $E(z) M_{500} > 2 \times 10^{14} h^{-1} M_\odot$. We conclude that if such a massive system is already present at $z=2$ it is extremely likely (90% probability accordingly to the MUSIC sample) that it just went through a major merger phase that generated strong shocks to heat the gas. This eventuality is not surprising from a theoretical point of view since the increase steepness of the mass function at 