Abstract: | Models that are able to reproduce the abundance and clustering of galaxies are based on a statistical match between halos (or subhalos) and galaxies at a given redshift. The observational data are then used to constrain the mass relation between halos and galaxies. These models have been widely used to predict cosmological parameters, star formation rates, merger rates, weak lensing signal, and to interpret the results of hydrodynamical simulations. I will first introduce and discuss this approach, pointing out its advantages and limitations. I will then argue that the evolution of satellite galaxies is the main unknown in these models, and is probably more complicated than what is usually assumed. For example, the stellar mass of a satellite galaxy might depend not only on its host subhalo mass, but also on the mass of its group, and on the time it first became a satellite. A new methodology will be presented that is capable of exploring the complex behavior of satellite galaxies in a relatively simple manner. Using this new approach we were able to compute the correlation functions for a very large number of models (~10^7), finding a large range of accepted models, much larger than previously claimed. The new method is useful for various clustering studies, including AGNs, HI gas, and high-redshift galaxies. |