Modelling the small-scale clustering of VIPERS galaxies in the HOD framework

The present work is intended as a contribution to help formulate a response to one of the most interesting and contemporary questions of astrophysics: what is the link between baryonic matter and dark matter? An extremely useful tool to investigate this relationship is the study of galaxy clustering within the haloes of dark matter in which these objects originated. Studying galaxy clustering means to statistically study their spatial properties, in the assumption that galaxies are a biased tracer of the mass distribution that hosts them. It is the modelling of this bias that is the real focus of the present Thesis work. This modelling will be achieved through the exploitation of the Halo Occupation Distribution (HOD) model. Unlike other similar models, the HOD allows to efficiently model clustering on small scales by introducing a 1halo term in the two-point correlation function of galaxies. The model is in fact able to take into account how the astrophysics of inter-galactic interactions modify the spatial distribution of galaxies in haloes. The HOD model presented here has been included in a set of free software libraries optimised for cosmological studies, called CosmoBolognaLib. Subsequently, the implemented model has been tested on data from the latest release of the VIPERS survey, for which the HOD has not yet been exploited. In this way it has been shown that the implementation presented here is effective, paving the way for a future application on data from completed or next-generation surveys, such as Euclid. Finally, we present an improvement to the model which, in the future, will make it possible to model the clustering of small-scale galaxies even better.