Large-scale galaxy distribution in the Las Campanas Redshift Survey

We make use of three-dimensional clustering analysis, inertia tensor methods, and the minimal spanning tree, technique to estimate some physical and statistical characteristics of the large-scale galaxy distribution and, in particular, of the sample of overdense regions seen in the Las Campanas Redshift Survey (LCRS). Our investigation provides additional evidence for a network of structures found in our core sampling analysis of the LCRS: a system of rich sheet-like structures, which in turn surround large underdense regions criss-crossed by a variety of filamentary structures. We find that the overdense regions contain similar to 40-50 per cent of LCRS galaxies and have proper sizes similar to those of nearby superclusters. The formation of such structures can be roughly described as a non-linear compression of protowalls of typical cross-sectional size similar to 20-25 h(-1) Mpc; this scale is similar to5 times the conventional value for the onset of non-linear clustering - to wit, r(0), the autocorrelation length for galaxies. The comparison with available simulations and theoretical estimates shows that the formation of structure elements with parameters similar to those observed is presently possible only in low-density cosmological models, Omega (m)h similar to 0.2-0.3, with a suitable large-scale bias between galaxies and dark matter.