Metal enrichment of the intracluster medium: A three-dimensional picture of chemical and dynamical properties

Abstract

We develop a model for the metal enrichment of the intracluster medium (ICM) that combines a cosmological non-radiative hydrodynamical N-body/SPH (smoothed particle hydrodynamic) simulation of a cluster of galaxies, and a semi-analytic model of galaxy formation. The novel feature of our hybrid model is that the chemical properties of the diffuse gas in the underlying simulation are dynamically and consistently generated from stars in the galaxies. We follow the production of several chemical elements, provided by low- and intermediate-mass stars, core collapse and Type Ia supernovae. We analyse the spatial distribution of metals in the ICM, investigate the way in which the chemical enrichment proceeds and use iron emissivity as a tracer of gas motions. The similar abundance patterns developed by O and Fe indicate that both types of supernovae pollute the ICM in a similar fashion. Their radial abundance profiles are enhanced in the inner in the last Gyr because of the convergence of enriched gas clumps to the cluster centre; this increment cannot be explained by the metal ejection of cluster galaxies which is quite low at the present epoch. Our results support a scenario in which part of the central intracluster gas comes from gas clumps that, in the redshift range of z∼ 0.2 to 0.5, have been enriched to solar values and are at large distances from the cluster centre (from ∼1 to 6 h-1 Mpc) moving at very high velocities (from ∼1300 to 2500 km s-1). The turbulent gas motions within the cluster, originated in the inhomogeneous gas infall during the cluster assembly, are manifested in emission-weighted velocity maps as gradients that can be as large as over distances of a few hundred kpc. Gradients of this magnitude are also seen in velocity distributions along sightlines through the cluster centre. Doppler shifting and broadening suffered by the Fe K α 6.7-keV emission line along such sightlines could be used to probe these gas large-scale motions when they are produced within an area characterized by high iron line emissivity.