Feedback Processes in the Early Universe

Abstract

Feedback effects due to massive stars and supernovae in the first objects are shown to strongly regulate both galaxy formation/evolution and the reionization process. Here we review the most important ones in some detail. We discuss how Type II supernovae can be used as tracers of the first objects and detected with NGST, for which we predict supernova number counts including the effects of gravitational lensing. Preliminary results on the formation of dust in the ejecta of supernovae of primordial composition are also presented. We finally turn to the consideration of the process of inhomogeneous reionization due to primordial stellar sources by means of high resolution numerical simulations, allowing for a self-consistent treatment of the above feedback processes. These simulations allow us to draw conclusions on the evolution and epoch of reionization and about the fate of reionizing objects. We conclude that a large fraction (~ 99%) of collapsed objects must be dark at redshift around eight.