Confronting cold dark matter cosmologies with strong clustering of Lyman break galaxies at z∼3

We perform a detailed analysis of the statistical significance of a concentration of Lyman break galaxies at z similar to 3 recently discovered by Steidel et al., using a series of N-body simulations with N = 256(3) particles in a (100 (h-1) Mpc)(3) comoving box. While the observed number density of Lyman break galaxies at z similar to 3 implies that they correspond to systems with dark matter halos of less than or similar to 10(12) M-., the resulting clustering of such objects on average is not strong enough to be reconciled with the concentration if it is fairly common; we predict one similar concentration approximately per 6-10 fields in three representative cold dark matter models. Considering the current observational uncertainty of the frequency of such clustering at z similar to 3, it would be premature to rule out the models, but the future spectroscopic surveys in a dozen fields could definitely challenge all the existing cosmological models a posteriori fitted to the z = 0 universe.