Simulated X-ray luminosities (0.5–2  keV) as a function of stellar mass for the most massive galaxies of simulation S230A and their counterparts in S230D, at redshift z = 0. The diamonds represent luminosities from the simulation, including metal cooling. The squares are the upper-limit observational estimates from Bogdán et al. (2015) in the same energy range. The luminosities (both observed and simulated) were measured within two regions: an inner annulus (upper frame) and an outer annulus (lower frame). For comparison, the small circles show the simulation estimates taking into account only the bremsstrahlung contribution.