Abstract:
A well-known problem with phenomenological (also called semi-analytical) galaxy formation models is the overabundance in the predictions of bright, blue galaxies. At late times the models produces too many stars. Two main classes of solutions to this problem are presented. The first solution is to form stars earlier, i.e. at high-redshifts. The second solution is to actually stop forming stars at late time, especially in overdense regions like galaxy clusters. Observational projects, desigend to test our new model ingredients that aim to stop forming too many stars, are presented as well.