The Lyα Forest from Gravitational Collapse in the Cold Dark Matter + Λ Model

We use an Eulerian hydrodynamic cosmological simulation to model the Lya forest in a spatially at, COBE-normalized, cold dark matter model with ) \ 0.4. We nd that the intergalactic, photoionized gas is predicted to collapse into sheetlike and lamentary structures which give rise to absorption lines having characteristics similar to the observed Lya forest. A typical lament is D500 h~1 kpc long with thickness D50 h~1 kpc (in proper units), and baryonic mass D1010 h~1