Statistical analyses of galaxy catalogues

Abstract

Galaxy catalogues, complete over a wide range of limiting magnitude, are statistically analysed to test theories of formation of galaxies and clusters of galaxies. Statistical measures used in the past to investigate the galaxy distribution in these catalogues are reviewed and the results there from summarised. From applying statistical techniques new to extra galactic astronomy to shallower catalogues it is found that the evidence supporting the hierarchical distribution of galaxies at small scale lengths is not as strong as previously believed. The results are more consistent with a model for galaxy distribution where galaxies are found in clusters with power-law profiles. The implications of this result for theories of galaxy formation are discussed. New, extensive catalogues, complete in J and R to faint limits are obtained from machine measurements of U.K. Schmidt photographs at the South Galactic Pole. The techniques required to produce these catalogues are described. Number magnitude counts and colour magnitude diagrams for these samples are presented and found to be consistent with the work of other authors. These results are used to investigate the selection effects operating in the samples. Tentative evidence for galaxy luminosity evolution is discussed. The strength of galaxy clustering in these deep catalogues is statistically measured and compared with the results from shallower surveys. From this comparison good evidence is found for the homogeneity of the galaxy distribution over the large scales 50-700 h(^-1) Mpc. None of the discrepancies of previous studies are found. The possibility of testing theoretically predicted clustering growth rates with such data is discussed. Statistical analysis of galaxies in the deep samples also shows evidence for a feature in the 2-point galaxy correlation function like that found in the analysis of shallower catalogues. However, the position of the feature corresponds to a spatial separation of 3 h(^-1) Mpc instead of 9 h(^-1) Mpc as found locally. The reasons for the discrepancy are discussed and the implications for galaxy formation theory described. Finally the faint stellar catalogues produced alongside the deep galaxy catalogues are statistically analysed. Evidence is found for two distinct populations of stellar types at the South Galactic Pole. The spatial distribution of stars within these populations is investigated.