Spatial structure of cosmic baryon distribution

The figures shows configurations enclosed by 3D isodensity contours at z=3. At low densities (first panel, overdensity = 0.1), the contours enclose isolated amorphous regions. These lie at the centers of minivoids, underdense regions a few (comoving) megaparsecs across, as shown in the second and third panels (overdensities = 0.3 and 0.5). The systems corresponding to the cosmological average density (overdensity = 1), in the fourth panel show a cell-like or spongy morphology, with underdense regions separated by wall-like partitions of varying thicknesses. The next panel (overdensity = 3), shows a filamentary network emerging from the intersections of the walls. The network, or cosmic web, is prominent in the final panel (overdensity = 10). (From Zhang, Meiksin, Anninos & Norman 1998.)