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

We develop a model to implement metal enrichment in a cosmological context based on the hydrodynamical code AP3MSPH described by Tissera, Lambas and A badi. The star formation model is based on the Schmidt law, and has been mo dified in order to describe the transformation of gas into stars in more de tail. The enrichment of the interstellar medium resulting from Type I and I I supernovae explosions is taken into account by assuming a Salpeter initia l mass function and different nucleosynthesis models. The various chemical elements are mixed within the gaseous medium according to the smooth partic le hydrodynamics technique. Gas particles can be enriched by different neig hbouring particles at the same time. We present tests of the code that asse ss the effects of resolution and model parameters on the results. We show t hat the main effect of low numerical resolution is to produce a more effect ive mixing of elements, resulting in abundance relations with less dispersi on. We have performed cosmological simulations in a standard cold dark matt er scenario, and we present results of the analysis of the star formation a nd chemical properties of the interstellar medium and stellar population of the simulated galactic objects. We show that these systems reproduce the a bundance ratios for primary and secondary elements of the interstellar medi um, and the correlation between the (O/H) abundance and the gas fraction of galaxies. We find that the star formation efficiency, the relative rate of Type II supernovae to Type I supernovac and the lifetime of binary systems , as well as the stellar nucleosynthesis model adopted, affect the chemical properties of baryons. We have compared the results of the simulations wit h an implementation of the one-zone simple model, finding significant diffe rences in the global metallicities of the stars and gas as well as their co rrelations with dynamical parameters of the systems. The numerical simulati ons performed provide a detailed description of the chemical properties of galactic objects formed in hierarchical clustering scenarios and prove to b e useful tools to deepen our understanding of galaxy formation and evolutio n.