Chemical evolution using smooth particle hydrodynamical cosmological simulations -- I. Implementation, tests and first results

Abstract

We develop a model to implement metal enrichment in a cosmological context based on the hydrodynamical AP3MSPH code described by Tissera, Lambas and Abadi (1997). The star formation model is based on the Schmidt law and has been modified in order to describe the transformation of gas into stars in more detail. The enrichment of the interstellar medium due to supernovae I and II explosions is taken into account by assuming a Salpeter Initial Mass Function and different nucleosynthesis models. The different chemical elements are mixed within the gaseous medium according to the Smooth Particle Hydrodynamics technique. Gas particles can be enriched by different neighbouring particles at the same time. We present tests of the code that assess the effects of resolution and model parameters on the results. We show that the main effect of low numerical resolution is to produce a more effective mixing of elements, resulting in abundance relations with less dispersion. We have performed cosmological simulations in a standard Cold Dark Matter scenario and we present results of the analysis of the star formation and chemical properties of the interstellar medium and stellar population of the simulated galactic objects. We show that these systems reproduce abundance ratios for primary and secondary elements of the interstellar medium, and the correlation between the (O/H) abundance and the gas fraction of galaxies. We find that star formation efficiency, the relative rate of supernovae II to supernovae I and life-time of binary systems as well as the stellar nucleosynthesis