Structure and formation of superclusters. XI. Voids, connectivity andmean density in the CDM universes.
Abstract
The evolution of structure in numerical simulations of flat CDM universes is discussed. The distribution of high-density regions is compared with the observed distribution of systems of galaxies in the region extending up to the nearest superclusters. The sizes of regions below a given threshold density (voids) and the connectivity properties of regions above a given threshold density (superclusters) are analysed. The distribution of galaxies is used to constrain the threshold density level and hence the amount of the CDM being hidden in voids in the different models adopted. The influence of large-scale modes in the adiabatic CDM spectrum is sufficiently strong to result in large bound objects and low-density regions already at the onset of the non-linear gravitational instability epoch. From this moment high-density systems remain connected, and the network of connected systems fills a very small fraction of space in contrast to random samples. High-density regions define the void probability function similar to the observed one. When the threshold density is too high, we exclude all matter in lower density filaments that join clusters, and bridges between clusters break up. In the CDM model with critical mass density {OMEGA} = 1, we must associate more than 40 per cent of all matter with systems of galaxies, if we want the connected structure to survive. A low-density model ({OMEGA}_0_ = 0.2) describes satisfactorily large voids and connected objects in our 'nearby' Universe and predicts that the density of matter associated with systems of galaxies in this region is about 0.10 -0.15.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- May 1990
- Bibcode:
- 1990MNRAS.244..214G
- Keywords:
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- Dark Matter;
- Density Distribution;
- Galactic Clusters;
- Galactic Evolution;
- Universe;
- Astronomical Models;
- Computational Astrophysics;
- Gravitational Effects;
- Probability Distribution Functions;
- Astrophysics