Evolution with redshift of the ICM abundances

Abstract

We predict the behaviour of the abundances of $α$-elements and iron in the intracluster medium as a function of redshift in poor and rich clusters. In order to do that we calculate the detailed chemical evolution of elliptical galaxies by means of one-zone and multi-zone models and then we integrate the contributions to the total gas and single elements by ellipticals over the cluster mass function at any given cosmic time which is then transformed into redshift according to the considered cosmological model. We refer to the one-zone model for ellipticals as to burst model and to the multi-zone model as to continuous model. We find that in the case of the burst model the ICM abundances should be quite constant starting from high redshifts ($z > 2$) up to now, whereas in the continuous model the ICM abundances should increase up to $z \sim 1$ and are almost constant from $z \sim 1$ up to $z=0$. Particular attention is devoted to the predictions of the $[α/Fe]_{ICM}$ ratio in the ICM: for the burst model we predict $[α/Fe]_{ICM}>0$ over the whole range of redshifts and in particular at $z =0$, whereas in the case of the continuous model we predict a decreasing $[α/Fe]_{ICM}$ ratio with decreasing $z$ and $[α/Fe]_{ICM} \le 0$ at $z= 0$. In particular, we predict $[O/Fe]_{ICM}(z=0) \le +0.35$ dex and $[Si/Fe]_{ICM}(z=0) \le +0.15$ dex for the bursts models and $[O/Fe]_{ICM}(z=0) \le -0.05$ dex and $[Si/Fe]_{ICM}(z=0) \le +0.13$ dex for the continuous models, the precise values depending on the assumed cosmology. Finally, we discuss the influence of different cosmologies on the results.