Weighing Superclusters
  We present a summary report on a detailed study of the mass and dynamical state of the Corona Borealis supercluster using the largest redshift survey of this object to date. Extensive $N$-body experiments are performed on simulated superclusters in both critically-flat and low-density cosmological models to test the robustness and errors of the mass estimators used on the data. From the redshifts and dynamics of 528 galaxies in the supercluster, the mass of Corona Borealis is estimated to be at least $3\times 10^{16} h^{-1} M_\odot$, and the mass-to-light ratio is $560 h (M/L)_\odot$, yielding a matter density parameter of $\Omega_m\approx 0.4$. We also discuss the prospects for mapping the mass distribution on supercluster scales with gravitational lensing. 
Chung-Pei Ma (U. Penn.), Todd A. Small (IoA, Cambridge), and Wallace   L. W. Sargent (Caltech)