Void Scaling and Void Profiles in CDM Models

Abstract

An analysis of voids using cosmological N-body simulations of cold dark matter models is presented. It employs a robust statistics of voids, that was recently applied to discriminate between data from the Las Campanas Redshift Survey and different cosmological models. Here we extend the analysis to 3D and show that typical void sizes D in the simulated galaxy samples obey a linear scaling relation with the mean galaxy separation lambda: D=D_0+nu*lambda. It has the same slope nu as in 2D, but with lower absolute void sizes. The scaling relation is able to discriminate between different cosmologies. For the best standard LCDM model, the slope of the scaling relation for voids in the dark matter halos is too steep as compared to the LCRS, with too small void sizes for well sampled data sets. The scaling relation of voids for dark matter halos with increasing mass thresholds is even steeper than that for samples of galaxy-mass halos where we sparse sample the data. This shows the stronger clustering of more massive halos. Further, we find a correlation of the void size to its central and environmental average density. While there is little sign of an evolution in samples of small DM halos with v_{circ} ~ 90 km/s, voids in halos with circular velocity over 200 km/s are larger at redshift z = 3 due to the smaller halo number density. The flow of dark matter from the underdense to overdense regions in an early established network of large scale structure is also imprinted in the evolution of the density profiles with a relative density decrease in void centers by 0.18 per redshift unit between z=3 and z=0.