Large Scale Structure



The large scale cosmic network consists of galaxy chains, clumps of galaxies representing groups and clusters, and void regions without bright galaxies. Structures on the larges scale are still representative for the cosmological origin near to the black hole.



Superclusters, Groups, and the Cosmic Web

Large supercluster stuctures (picture left) and fine group structures (picture right) are gained from a large redshift survey of galaxies, the 2-Degree Galaxy Redshift Survey (2dFGRS). Special technics were employed for uniformly extracting structures near to the observer (at the central point in the double cone diagram) and far away in the deep universe (at the upper and lower parts of the slice trough the survey volume). The left picture shows a couple of superclusters (red regions) and a connected underlying underdense region (blue regions).

Supercluster density field of
   2dFGRS Groups density field of 
   2dFGRS

Voids and the Local Universe

A catalogue of voids was extracted from the 2dFGRS. Here we show here the 100 biggest voids as spherical regions. Surprisingly they are all of comparable size. Some galaxies are projected into the void regions due to the finite thickness of the survey volume. The void phenomenon is a sensitive test of the underlying cosmological model. We also identified faint galaxies in voids defined by bright galaxies. They show typically more blue than red colors and higher star formation rates as judged by the sprectral properties. Explaining these differences is the aim of our galaxy formation simulations.

Cosmological simulations cover a large dynamical and mass range. A representative volume must enclose several billion light years, whereas the inner structure of galaxies must be resolved on scales of a few 100 light years. Most massive clusters containing thousands of galaxies should be resolved together with dwarf galaxies. This is far from present possibilities even on the largest supercomputers. To tackle this problem we use smaller simulation boxes specifically designed to represent the observed local universe. There, we can identify well known massive structures as nearby clusters (Coma, Virgo, Perseus Pices, Great Attractor), but also the local group in the right environment and infalling towards Virgo. Within the simulated local group candidate we found three galaxies which may represent Milky Way, Andromeda (M31) and M33. In our simulation we have resolved the local group with several million particles.

Satellite orbit around a dark
   matter halo Satellite orbit around a dark
   matter halo

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