Figure 11: Distribution of the gas density at redshift from a numerical hydrodynamics simulation of the Ly forest with a CDM spectrum normalized to second year COBE observations, Hubble parameter of , a comoving box size of 9.6 Mpc, and baryonic density of composed of 76% hydrogen and 24% helium. The region shown is 2.4 Mpc (proper) on a side. The isosurfaces represent baryons at ten times the mean density and are color coded to the gas temperature (dark blue = 3 × 10⁴ K, light blue = 3 × 10⁵ K). The higher density contours trace out isolated spherical structures typically found at the intersections of the filaments. A single random slice through the cube is also shown, with the baryonic overdensity represented by a rainbow-like color map changing from black (minimum) to red (maximum). The He⁺ mass fraction is shown with a wire mesh in this same slice. To emphasize fine structure in the minivoids, the mass fraction in the overdense regions has been rescaled by the gas overdensity wherever it exceeds unity.