The recycling of gas and metals in galaxy formation: predictions of a dynamical feedback model

We present results of a new feedback scheme implemented in the Munich galaxy formation model. The new scheme includes a dynamical treatment of galactic winds powered by supernova explosions and stellar winds in a cosmological context. We find that such a scheme is a good alternative to empirically motivated recipes for feedback in galaxy formation. Model results are in good agreement with the observed luminosity functions and stellar mass function for galaxies in the local universe. In particular, the new scheme predicts a number density of dwarfs that is lower than in previous models. This is a consequence of a new feature of the model, which allows an estimate of the amount of mass and metals that haloes can permanently deposit into the intergalactic medium (IGM). This loss of material leads to the suppression of star formation in small haloes and therefore to the decrease in the number density of dwarf galaxies. The model is able to reproduce the observed mass-stellar metallicity and luminosity-gas metallicity relationships. This demonstrates that our scheme provides a significant improvement in the treatment of the feedback in dwarf galaxies. Despite these successes, our model does not reproduce the observed bimodality in galaxy colours and predicts a larger number of bright galaxies than observed. Finally, we investigate the efficiency of metal injection in winds and in the IGM. We find that galaxies that reside in haloes with M-vir < 10(12) h(-1) M-circle dot may deposit most of their metal mass into the IGM, while groups and clusters at z = 0 have lost at most a few per cent of their metals before the bulk of the halo mass was accreted.