Voids in the Simulated Local Universe

Abstract

We use simulations of the formation and evolution of the galaxy population in the Local Universe to address the issue of whether the standard theoretical model succeeds in producing empty regions as large and as dark as the observed nearby ones. We follow the formation of galaxies in an LCDM universe and work with mock catalogues which can resolve the morphology of LMC sized galaxies, and the luminosity of objects 6 times fainter. We look for a void signature in sets of virialized haloes selected by mass, as well as in mock galaxy samples selected according to observationally relevant quantities, like luminosity, colour, or morphology. We find several void regions with diameter 10 Mpc/h in the simulation where gravity seems to have swept away even the smallest haloes we were able to track. We probe the environment density of the various populations and compute luminosity functions for galaxies residing in underdense, mean density and overdense regions. We also use nearest neighbour statistics to check possible void populations, taking $L_{*}$ spirals as reference neighbours. Down to our resolution limits, we find that all types of galaxies avoid the same regions, and that no class appears to populate the voids defined by the bright galaxies.