The distribution of galaxies in the direction of the 'Great Attractor'

Abstract

THE discovery of galaxy streaming motions of up to 600 km s−1 towards Hydra–Centaurus has led to the suggestion1 that this motion is induced by a concentration of galaxies (the 'Great Attractor') centred on galactic coordinates l = 307°, b = 9° at a distance corresponding to 4,350 ± 350 km s−1 in the Hubble Flow. Here we present a map of ~17,000 galaxies down to BJ = 17m in an extended region of the sky in this direction. The clusters of galaxies identified from the map are shown to constitute two distinct concentrations in redshift (see, for example, ref. 2). We explore the possibility that the further of the two concentrations, centred near l = 312°, b = 31°, at a mean redshift of 14,000 km s−1, is a major contributor to the peculiar motion of the Local Group. This is unlikely because the contribution to the dipole anisotropy of extragalactic light due to galaxies in this region, beyond a diameter limit of 1.3 arcmin, is about 10% of that due to nearer galaxies, and the concentration would need to have an extremely high mass-to-light ratio. Superclusters as massive as this would cause appreciable anisotropies in the cosmic microwave background radiation.