Simulation Studies of the Connection between Cosmic Void Evolution and Star Formation

To deepen our understanding of the creation and evolution of the largest structures in our Universe, the cosmic web made up of galaxies and voids, the void model can be used to explain the matter inflow in galaxies needed for stars to form. In contrast to using the idea of dark matter halos accreting mass to form galaxies, the void model could potentially give a simpler description. When a void, an under-dense region in the matter distribution, expands it creates a ridge of matter in its outer layer that can be seen as a mass flow giving rise to a mass flow rate (MFR) out of the void. This matter is what flows into close-by galaxies, giving rise to star formation. The MFR can therefore be compared to the SFR (Star Formation Rate) of these close by galaxies. This study aims to explore whether the void model can be used to describe galaxy- and star formation in the Universe, and if it is possible to find a parameter to describe the relation between the gas flow from the void model and the star formation in galaxies from N-body simulations. The Void IDentification and Examination Toolkit (VIDE) was used to identify voids from the cosmological hydrodynamical simulation Horizon-AGN, with the COSMOS filter. The standard ΛCDM cosmology WMAP-7 was used. Cuts were made on the core density as well as position of the voids. All galaxies having a radial distance to the void-center of void radius ± ∆r were matched. In this study, the choice of ∆r should be treated as a free parameter. The correlation between the MFR from voids and SFR in nearby galaxies obtained suggests that the void model can be used to describe star formation. The results matches well with observational data and quite well with theoretical numerical solutions for z > 1. A relation between the SFR and MFR have been obtained in the time dependent parameter ε. The void model can be explored further by using theoretical obtained values for ∆r to explain the extent of the mass flow from voids.