Clusters, superclusters, and large-scale structure: a consistent picture.

Observations of the large-scale structure in the universe using different tracers and techniques, including the spatial distribution of galaxies, clusters of galaxies, narrow pencil-beam surveys, and quasars, appear to be yielding a consistent picture of the universal structure. A network of large-scale superclusters with scales up to approximately 150h-1 Mpc is suggested (where h approximately 0.5-1 is the Hubble constant in units of 100 km.s-1.Mpc-1; 1 pc = 3.09 x 10(16) m; h = 1 is used throughout this paper). The supercluster network surrounds low-density regions, suggesting a "cellular" structure of the universe. The universal dimensionless cluster correlation function, supported by new data from automated cluster surveys, is consistent with this picture. The "standard" Omega = 1 cold dark matter (CDM) model for the universe appears to be inconsistent with the details of the observed large-scale structure distribution; a low-density, Omega approximately 0.2-0.3, CDM model provides a considerably better fit to the observations.