The MUSIC of Galaxy Clusters II: X-ray global properties and scaling relations

We present the X-ray properties and scaling relations of a large sample of clusters extracted from the Marenostrum MUltidark SImulations of galaxy Clusters (MUSIC) data set. We focus on a sub-sample of 179 clusters at redshift z similar to 0.11, with 3.2 x 10(14) h(-1) M-circle dot < M-vir < 2 x 10(15) h(-1) M-circle dot, complete in mass. We employed the X-ray photon simulator PHOX to obtain synthetic Chandra observations and derive observable-like global properties of the intracluster medium (ICM), as X-ray temperature (T-X) and luminosity (L-X). T-X is found to slightly underestimate the true mass-weighted temperature, although tracing fairly well the cluster total mass. We also study the effects of T-X on scaling relations with cluster intrinsic properties: total (M-500 and gas M-g,M-500 mass; integrated Compton parameter (Y-SZ) of the Sunyaev-Zel'dovich (SZ) thermal effect; Y-X = M-g,M-500 T-X. We confirm that Y-X is a very good mass proxy, with a scatter on M-500-Y-X and Y-SZ-Y-X lower than 5 per cent. The study of scaling relations among X-ray, intrinsic and SZ properties indicates that simulated MUSIC clusters reasonably resemble the self-similar prediction, especially for correlations involving T-X. The observational approach also allows for a more direct comparison with real clusters, from which we find deviations mainly due to the physical description of the ICM, affecting T-X and, particularly, L-X.