Detection of structures on multiple scales around the South Galactic Pole

A two-dimensional analysis of the COSMOS/UKST Southern Sky Galaxy Catalogue

Royal Observatory, Blackford Hill, Edinburgh, EH9 3HJ, UK

Send offprint request to: Harvey T. MacGillivray

Received: 26 June 1995
Accepted: 14 December 1995

Abstract

We report the results of a 2D analysis of distributions of galaxies in a search for structures on a wide range of scales, from clusters up to superclusters and beyond, including the identification of voids. The structures are identified in data from the COSMOS/UKST Southern Sky Galaxy Catalogue (CUSSGC). The subsample used in this first investigation contains some galaxies in an area of degrees around the South Galactic Pole. From our analysis, we find 25 very large-scale structures (of 10 degrees or more in extent), about 60 structures of intermediate scales (superclusters and/or elongated features), and more than 220 cluster-sized objects. All these features are significant, having high confidence levels for detection. Some extended voids are also detected in this area, likewise with high significance. This work is based on the use of the wavelet transform, the method of which has already been extensively described in a previous paper in which we demonstrated the principle of the technique. The wavelet analysis gives the position of the structures detected, together with significance levels and some parametrisation of their properties (extent, population, elongation, etc). Ultimately, our aim is the construction of a large and homogeneous database of structures on all scales in this important part of the southern sky.