The Shapley Supercluster. I. Spectroscopic Observations in the Central Region

We present a new analysis of the kinematics of the Shapley supercluster based on radial velocities for 1087 galaxies in the clusters A3558 (Shapley 8), A3528 (Klemola 21), A3532 (Klemola 22), A3530, A3556 (SC 1321-314), A3559 (CE 1327-292), A3560, A3562, SC 1329-314 and in the intercluster region of the core of the supercluster, of which 367 are new measurements. We also present accurate positions from APM and MAMA scans of the ESO/SERC Southern Sky Survey photographic plates. We obtain new velocity dispersions and estimate the masses of the member clusters, evaluating dynamical models of the supercluster. The supercluster is found to be significantly flattened. We find that for OMEGA₀_ = 0. 3, H₀_= 75 km s^-1^ Mpc^-1^, the gravitational pull of the supercluster may account for up to 25% of the peculiar velocity of the Local Group required to explain the dipole anisotropy of the Cosmic Microwave Background radiation, in which case the mass of the supercluster would be dominated by intercluster dark matter. This fractional contribution would be considerably higher for combinations of significantly lower values of OMEGA₀_ and higher values of H₀_.