Intergalactic baryon-rich regions at high redshift
  Using a high resolution cosmological simulation of reionization we have examined the differing structures formed by gas and dark matter at a redshift of 5.1. Baryon-rich regions form a small number of filaments, which connect the largest galaxies in the simulation. More detailed examination of the ten largest galaxies reveals long, slender gaseous filaments about 5 proper kpc in width radiating from the galaxy centers. Extending out from each filament are a few smooth, thin, nearly planar gaseous sheets. By contrast, the dark matter concentrates into quasi-spherical bodies. The results have implications for our understanding of structure formation in the early universe and of the Lyman alpha forest. 
A. Gayler Harford (JILA), Andrew J. S. Hamilton (JILA), Nickolay Y.   Gnedin (Fermilab)