Towards understanding the structure of voids in the cosmic web

TL;DR

This paper investigates how different scale density waves combine to form cosmic voids, revealing that large voids require a spectrum of primordial perturbations and involve synchronized density fluctuations.

Contribution

It demonstrates the necessity of an extended spectrum of primordial density perturbations for the formation of large multi-scale voids in the cosmic web.

Findings

Small haloes form with perturbations up to 8 Mpc/h

Large voids need extended spectrum of density perturbations

Void formation involves synchronization and suppression of galaxy formation

Abstract

Our goal is to see how density waves of different scale combine to form voids between galaxy systems of various scale. We perform numerical simulations of structure formation in cubes of size 100 and 256 Mpc/h, with resolutions 256^3 and 512^3 particles and cells. To understand the role of density perturbations of various scale we cut power spectra at scales from 8 to 128 Mpc/h, using in all series identical initial random realisations. We find that small haloes and short filaments form all over the simulation box, if perturbations only up to scale 8 Mpc/h are present. The phenomenon of large multi-scale voids in the cosmic web requires the presence of an extended spectrum of primordial density perturbations. The void phenomenon is due to the action of two processes: the synchronisation of density perturbations of medium and large scales, and the suppression of galaxy formation in low-density regions by the combined action of negative sections of medium- and large-scale density perturbations, so that their densities are less than the mean density, and thus during the evolution their densities decrease.