On the dynamical origin of the ICM metallicity evolution

Abstract

We present a study on the origin of the metallicity evolution of the intra-cluster medium (ICM) by applying a semi-analytic model of galaxy formation to N-body/smoothed particle hydrodynamic (SPH) non-radiative numerical simulations of clusters of galaxies. The semi-analytic model includes gas cooling, star formation, supernovae feedback and metal enrichment, and is linked to the diffuse gas of the underlying simulations so that the chemical properties of gas particles are dynamically and consistently generated from stars in the galaxies. This hybrid model lets us have information on the spatial distribution of metals in the ICM. The results obtained for a set of clusters with virial masses of ∼1.5 × 1015 h−1 M contribute to the theoretical interpretation of recent observational X-ray data, which indicate a decrease of the average iron content of the intra-cluster gas with increasing redshift. We find that this evolution arises mainly as a result of a progressive increase of the iron abundance within ∼0.15 Rvir. The clusters have been considerably enriched by z ∼ 1 with very low contribution from recent star formation. Low entropy gas that has been enriched at high redshift sinks to the cluster centre contributing to the evolution of the metallicity profiles.