[Paper Review] The Edinburgh/Durham Southern Galaxy Catalogue - IX. The Galaxy Catalogue

R. C. Nichol, C. A. Collins+1 more|arXiv (Cornell University)|Aug 11, 2000

Astronomy and Astrophysical Research1 references3 citations

TL;DR

This paper presents the public release of the Edinburgh/Durham Southern Galaxy Catalogue (EDSGC), a large-scale, digitized galaxy survey of 1,495,877 galaxies across 1,182 deg² centered on the South Galactic Pole, using photographic plates from the UK Schmidt Telescope and the COSMOS micro-densitometer. The catalogue provides high-precision $b_j$ photometry with plate-to-plate accuracy of $\Delta b_j \simeq 0.1$, validated by spectroscopic checks showing only 12% star-galaxy misclassification, making it ideal for large-scale structure and cosmological studies.

ABSTRACT

We announce here the public availability of the Edinburgh/Durham Southern Galaxy Catalogue (EDSGC, http://www.edsgc.org). This objective galaxy catalogue was constructed using the COSMOS micro-densitometer at the Royal Observatory Edinburgh and constitutes one of the largest digitized galaxy surveys currently in existence. The EDSGC contains a total of 1,495,877 galaxies (each with 27 image parameters) covering an contiguous area of 1182 sq deg centered on the South Galactic Pole. The data consists of photographic bj magnitudes calibrated via CCD sequences which provide a plate-to-plate accuracy of bj~0.1. Extensive external checks have demonstrated that the global EDSGC photometry is free of large-scale systematic gradients and is therefore, ideal for studying the distribution of galaxies on large angular scales. Independent spectroscopy of EDSGC galaxies has shown that the accuracy of the star-galaxy separation is consistent with earlier visual checks and that only 12% of EDSGC galaxies are potentially mis-classified. This paper is intended to provide a summary of the essential details of the catalogue's design and construction as well as provide a brief summary of the main scientific achievements using the EDSGC over the last ten years.

Motivation & Objective

• To create a comprehensive, objective, and publicly available galaxy catalogue from digitized photographic plates for cosmological research.
• To ensure high photometric accuracy and minimal systematic gradients across the survey area to support large-scale structure analysis.
• To validate the reliability of automated galaxy detection and star-galaxy separation in a large-scale survey.
• To provide a foundational object catalogue for subsequent redshift surveys, such as the ESO Slice Project and the Durham/UKST Galaxy Redshift Survey.
• To enable robust statistical studies of galaxy clustering, luminosity functions, and cluster properties using a homogeneous, well-calibrated dataset.

Proposed method

• Digitization of UK Schmidt Telescope IIIa-J plates using the COSMOS micro-densitometer at the Royal Observatory Edinburgh.
• Photometric calibration of $b_j$ magnitudes using CCD sequences to achieve $\Delta b_j \simeq 0.1$ plate-to-plate accuracy.
• Application of automated deblending algorithms to resolve closely spaced galaxies and improve source fidelity.
• Use of visual and spectroscopic checks to validate star-galaxy separation, with independent confirmation from the ESO Slice Project.
• Implementation of extensive external checks to verify the absence of large-scale photometric gradients and systematic errors.
• Integration of the EDSGC as the parent catalogue for major redshift surveys, enabling cross-validated cosmological analysis.

Experimental results

Research questions

• RQ1 What is the photometric accuracy and systematic stability of a large-scale, digitized galaxy survey like the EDSGC across a contiguous 1,182 deg² area?
• RQ2 How reliable is the automated star-galaxy separation in the EDSGC, and how does it compare to visual and spectroscopic checks?
• RQ3 To what extent does the EDSGC reproduce the large-scale clustering patterns observed in other surveys like APM, and how does it compare to N-body simulations?
• RQ4 What insights does the EDSGC provide into the luminosity function and spatial distribution of galaxies and clusters on scales up to 140 h⁻¹ Mpc?
• RQ5 How well does the EDSGC support cosmological inference when used as a parent catalogue for redshift surveys such as the ESO Slice Project?

Key findings

• The EDSGC contains 1,495,877 galaxies with 27 image parameters each, covering 1,182 deg² centered on the South Galactic Pole with high photometric precision.
• Photometric calibration achieves a plate-to-plate accuracy of $\Delta b_j \simeq 0.1$, and external checks confirm the absence of large-scale systematic gradients.
• Spectroscopic validation from the ESO Slice Project shows only 12% of EDSGC galaxies are misclassified as stars, confirming the reliability of automated star-galaxy separation.
• The angular correlation function of the EDSGC confirms the high amplitude found in the APM survey and corrects earlier errors in the Lick catalogue results.
• The EDSGC enabled key redshift surveys, including the 85% complete ESP survey of ~3,300 galaxies to $b_j = 19.4$, revealing a local underdensity out to ~140 h⁻¹ Mpc.
• The EDSGC supports robust cosmological inference, including the detection of excess power in galaxy clustering and velocity dispersion on 50–100 h⁻¹ Mpc scales, inconsistent with standard cold dark matter models.