Voids in the simulated local Universe

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 those observed nearby. We follow the formation of galaxies in a cold dark matter universe and work with mock catalogues that can resolve the morphology of Large Magellanic Cloud sized galaxies, and the luminosity of objects six times fainter. We look for a void signature in sets of virialized haloes selected by mass, and in mock galaxy samples selected according to observationally relevant quantities, such as luminosity, colour or morphology. We find several void regions with diameter 10 h -1 Mpc in the simulation where gravity seems to have swept away even the smallest haloes we were able to track. We probe the environment density for 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.