Speaker
Description
The clustering of large-scale structures is recognised as a fundamental cosmological probe, offering us the possibility to constrain fundamental parameters such as the matter density content of the Universe. Currently, the most acknowledged cosmological scenario is the ΛCDM model, which assumes that dark matter particles exist in a ‘cold' version, namely in the form of very massive candidates, e.g. WIMPs, or condensates of light axions. It is consistent with observations on scales ranging from the size of the cosmological horizon to the typical intergalactic distances. However, observations at typical galactic and sub-galactic scales, on the order of kpc, have suggested some possible tensions related to the number of satellite galaxies and halo density profiles. One possible solution is provided by complex baryonic feedback. Another possibility is to explore the dark sector, by investigating the macroscopic consequences of alternative cosmological scenarios based on the existence of warm dark matter (WDM) or self-interacting dark matter (SIDM) particles.
In this talk, we analyze some of the macroscopic consequences of alternative dark matter models. In particular, the free streaming of WDM particles on average suppresses the formation of the smallest halos, whereas the most massive perturbations are still able to collapse. This results in a general delay of early galaxy formation and in a reduction of the number density of faint galaxies, which directly impact the timeline of the Reionization process, a fundamental phase transition in the history of the Universe, during which the Intergalactic Medium (IGM) became ionized and therefore transparent to UV photons.
We also analyze the statistical properties and spatial distribution of dark matter halos. For this reason, we make use of the AIDA simulations, a set of dark matter-only boxes of different sizes and resolutions. For each cosmological scenario, we characterize the radial distribution of satellites, finding that a NFW model is not accurate enough to describe the density profile of subhalos. We also adopt the halo occupation distribution (HOD) formalism to model the abundances and the clustering properties of halos in both cold and different WDM and SIDM models. In particular, we find that the small-scale clustering of dark matter halos provides a valid way to discriminate between different cosmological scenarios, in preparation for a more detailed study that fully incorporates baryonic effects, and for a comparison with observational data from galaxy clustering.
