The Large Scale Distribution of Galaxies in the Shapley Supercluster

Abstract

We present new results of our wide-field redshift survey of galaxies in a 182 square degree region of the Shapley Supercluster (SSC) based on observations with the FLAIR-II spectrograph on the UK Schmidt Telescope (UKST). In this paper we present new measurements to give a total sample of redshifts for 710 bright (R ≤ 16.6) galaxies, of which 464 are members of the SSC (8000 < v < 18 000 km s^–1). Our data reveal that the main plane of the SSC (v ≈ 14 500 km s^–1) extends further than previously realised, filling the whole extent of our survey region of 10 degrees by 20 degrees on the sky (35 Mpc by 70 Mpc, for H₀ = 75 km s^–1 Mpc^–1). There is also a significant structure associated with the slightly nearer Abell 3571 cluster complex (v ≈ 12 000 km s^–1) with a caustic structure evident out to a radius of 6 Mpc. These galaxies seem to link two previously identified sheets of galaxies and establish a connection with a third one at V (vBar) = 15 000 km s^–1 near RA = 13^h. They also tend to fill the gap of galaxies between the foreground Hydra-Centaurus region and the more distant SSC. We calculate galaxy overdensities of 5.0 ± 0.1 over the 182 square degree region surveyed and 3.3 ± 0.1 in a 159 square degree region excluding rich clusters. Over the large region of our survey the inter-cluster galaxies make up 46 per cent of all galaxies in the SSC region and may contribute a similar amount of mass to the cluster galaxies.