Objective-prism and slit-spectra redshifts in a study of the distribution of galaxies
Abstract
A thorough and detailed investigation into the accuracy,
reliability and consistency of the objective-prism redshift technique
with changes in plate material, measuring machine and reduction
techniques has been undertaken. Providing that the limitations of the
procedures involved are appreciated, useful 3-D information, accurate
to Z ~±0.01, for large numbers of faint galaxies may be obtained from
single UKST fields. A surface brightness correction has enabled the
technique to be extended to galaxies as bright as bj ~15.8. The
validity of the results were confirmed by external calibration with
slit-spectra. The slit-spectra results obtained have more than
doubled the size of the calibration sample available and have further
vindicated the applicability of the technique.
Analysis of the 107 slit-spectra redshifts determined revealed
the existence of considerable structure in the field studied, with
significant density enhancements and voids being apparent. This
structure has been confirmed on larger scales and to greater depths
with the subsequent analysis of ~1,500 objective-prism redshifts from
COSMOS data of the field. Two large superclusters were discovered.
The first centred at Z ~0.05 but extending for at least 150 h⁻¹Mpc,
and the second a projected filament of connecting clusters at Z ~0.11
and 23 h⁻¹Mpc long. A selection of 2-D and 3-D statistical analysis
techniques have been used to describe the observed large-scale galaxy
distribution in this field.
A by-product of this work has been the discovery of a new and
powerful means of star/galaxy separation based on magnitude
comparisons between paired objects from both the direct and
objective-prism plates. This technique has revealed ~20% stellar
contamination in the star/galaxy separation based on direct plate data alone. In conclusion, objective-prism galaxy redshifts are valuable
information for complementing 2-D data in the study of the large-scale
distribution of galaxies from COSMOS measures of Large numbers of UKST
plates. To this end an automatic technique of objective-prism
redshift determination should be developed.
Type
Thesis, PhD Doctor of Philosophy
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http://creativecommons.org/licenses/by-nc-nd/4.0/
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