CLUSTERS, SUPERCLUSTERS, AND LARGE-SCALE STRUCTURE - A CONSISTENT PICTURE

Observations of the large-scale structure in the universe using differ ent tracers and techniques, including the spatial distribution of gala xies, clusters of galaxies, narrow pencil-beam surveys, and quasars, a ppear to be yielding a consistent picture of the universal structure. A network of large-scale superclusters with scales up to almost-equal- to 150h-1 Mpc is suggested (where h almost-equal-to 0.5-1 is the Hubbl e 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 lo w-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 pi cture. 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 almost-equal- to 0.2-0.3, CDM model provides a considerably better fit to the observ ations.