The Durham/UKST Galaxy Redshift Survey - I. Large-scale structure in the Universe

Abstract

We present the first results from the Durham/UKST Galaxy Redshift Survey and consider their implications on current models of structure formation. This bJ ≤ 17 mag survey contains ∼ 2500 galaxy redshifts sampled at a rate of 1 in 3 from the Edinburgh/Durham Southern Galaxy Catalogue. We find that the galaxy distribution shows evidence of large 'cellular' features on 50-100 h-1 Mpc scales. This clustering has been statistically analysed using the 2-point correlation function, ξ. The results show that the structures in this survey have power significantly in excess of the predictions of the standard cold dark matter (CDM) cosmological model on scales of 15-30 h-1 Mpc, and therefore support the previous observational results from the APM survey. At smaller scales, we measure the one-dimensional pairwise galaxy velocity dispersion in the Durham/UKST survey to be 387-62 +96 km s-1. This is also inconsistent with the prediction of the standard CDM model, assuming linear biasing. Finally, at larger scales, the Durham/UKST survey has produced the most accurate detection yet of large-scale redshift space distortions due to dynamical infall of galaxies. We obtain a best estimate of Ω0.6/b = 0.55 ± 0.12, where Ω is the mean mass density of the Universe and b is the linear bias factor. Depending on the choice of b, this result is consistent either with a low-density universe (b ≃ 1) or a critical-density universe (b ≃ 2).