The large-scale galaxy distribution in the halo model

Abstract

In the Halo Model (HM), the fundamental objects that we employ to describe matter distribution in the Universe are the structures which have already experience gravitational collapse: galaxy clusters, galaxy groups, even field galaxies. From a cosmological perspective, the large-scale structure of the Universe is characterized by the positions and velocities of those collapsed regions. Since dark matter constitutes the vast majority of matter in those structures, the dark matter halos are the building blocks, while galaxies are considered to follow (or "trace") the density profiles of those dark matter halos, according to some phenomenological distributions called Halo Occupation Distributions (HODs). This framework is powerful because it relates the basic objects in the theory of large-scale structure (halos) with the observed objects (galaxies), at the same time that it separates the large-scale regime (where the correlations between halo positions and velocities is key) from the small-scale regime (where the density profile of halos reflects other physical effects, including non-linear physics). The goal of this project is to study this description for the galaxy distribution in the Universe. The main application, which will be developed more towards the final stages of the project, will be to compare measurements of the power spectrum using halos and using galaxies, in the context of simple simulations (lognormal mocks). If possible, we will also employ some simple dataset based on a real survey. (AU)