The Norris Survey of the Corona Borealis Supercluster. III. Structure and Mass of the Supercluster

(Abridged) We present a study of the structure and dynamics of the CoronaBorealis Supercluster (z ~ 0.07) based on the redshifts for 528 galaxies in thesupercluster. The galaxy distribution within Corona Borealis is clumpy andappears overall to be far from relaxed. A background supercluster at z ~ 0.11makes a substantial contribution to the projected surface density of galaxiesin the Corona Borealis field. In order to estimate the mass of thesupercluster, we have assumed that the mass of the supercluster is proportionalto v^2r, where v and r are suitable scale velocity and radius, respectively,and we have used N-body simulations of both critical- and low-density universesto determine the applicability of standard mass estimators based on thisassumption. Although superclusters are obviously not in equilibrium, oursimulations demonstrate that the virial mass estimator yields mass estimateswith an insignificant bias and a dispersion of only ~25% for objects withoverdensities >~ 5. Non-uniform spatial sampling can, however, cause systematicunderestimates by as much as 30%. All of our simulated superclusters turn outto be bound, and based on the overdensity of the Corona Borealis supercluster,we believe it is also very likely to be bound and may well have started tocollapse. The mass of Corona Borealis is at least 3 x 10^16 solar masses, whichyields a B(AB)-band mass-to-light ratio of 564h (M/L)_solar on scales of ~20h^-1 Mpc. The background supercluster has a mass-to-light ratio of 726h(M/L)_solar. By comparing the supercluster mass-to-light ratios with thecritical mass-to-light ratio required to close the universe, we determine thatOmega_0 >~ 0.4 on supercluster scales.Comment: 29 pages with 8 figures included, to appear in ApJ, Jan 1, 199