Galaxy correlations on large scales

Abstract

We present our first results on large-scale structure in the Universe from a uniform survey of ≳ 2 million galaxies brighter than bJ = 20.5 constructed from machine scans of 185 UK Schmidt plates. We show that over a range of three magnitudes the galaxy two-point angular correlation function, w(θ), scales with depth as expected if we are measuring real clustering in the galaxy distribution. Our correlation functions show a break from a power law at roughly the same physical separation as found by Groth & Peebles from their analysis of the Lick catalogue, but our measurements decline much more gently from a power law on larger scales. We argue that Groth & Peebles may have removed some intrinsic clustering when they corrected for large-scale gradients in the Lick counts. Our analysis has important implications for theories of the formation of large-scale structure. In particular, our results imply more large-scale clustering than predicted by popular versions of the Cold Dark Matter cosmogony.