Evolution of the metal content of the intracluster medium with hydrodynamical simulations

We present a comparison between simulation results and X-ray observational data on the evolution of the metallicity of the intracluster medium (ICM). The simulations of galaxy clusters have been carried out using a version of the TREE PM-smoothed particle hydrodynamics (SPH) GADGET-2 code that includes a detailed model of chemical evolution by assuming three different shapes for the stellar initial mass function (IMF). Besides the Salpeter IMF, we also used the IMF proposed by Kroupa and the top-heavier IMF by Arimoto and Yoshii. We find that simulations predict significant radial gradients of the Iron abundance, Z(Fe), which extend over the whole cluster virialized region. Using the Salpeter IMF, the profiles of ZFe have an amplitude which is in a reasonable agreement with Chandra observations within 0.2R(500). At larger radii, we do not detect any flattening of the metallicity profiles. As for the evolution of the ICM metal abundance out to z = 1, it turns out that the results based on the Salpeter IMF agree with observations. We find that the evolution of Z(Fe) in simulations is determined by the combined action of (i) the sinking of already enriched gas, (ii) the ongoing metal production in galaxies and (iii) the locking of ICM metals in newborn stars. As a result, rather than suppressing the metallicity evolution, stopping star formation at z = 1 has the effect of producing an even too fast evolution of the emission-weighted ICM metallicity, with too high values of ZFe at low redshift within 0.2R(200). Finally, we compare simulations with the observed rate of Type Ia supernovae per unit B-band luminosity (SnUB). We find that our simulated clusters do not reproduce the decreasing trend of SnUB at low redshift, unless star formation is truncated at z = 1.