X-ray galaxy cluster and the cosmic star formation rate

We use current semi-analytic models of early star and galaxy formation, based upon the hierarchical growth of dark matter halos, to predict the amount and physical state of the hot baryons emitting X-rays in groups and clusters of galaxies. We relate the X-ray properties of such baryons to those of the star and cold gas content of the same halos. The model include the gas cooling, the infall of outer gas into the gravitational potential wells of the halos, the preheating and expulsion cold gas due to the energy fed back by the Supernovae which follow the star formation. We show that the amount of the hot phase required by the current star formation models is enough to be observable out to redshifts z approximate to 1.5 in forthcoming deep surveys from Chandra and XMM especially in case the star formation rate is high at such, and flat toward earlier z. These X-ray emissions constitute a necessary counterpart, and will provide a much wanted probe of the SF process itself, and in particular of the Supernovae feedback, to parallel and complement the currently debated data from optical and IR observations of the young stars.