Cooke, John Alan

2018-05-22T12:49:02Z

2018-05-22T12:49:02Z

1980

Since Hubble's discovery of the correlation between galaxy radial velocity and distance, velocities of galaxies have been obtained using slit spectra to establish the value of the Hubble constant. More recently, with the acceptance of a general Hubble flow, velocities have also been used to examine the distribution of galaxies in space. Velocities within clusters of galaxies have also been used to establish cluster velocity dispersions, and hence uirial masses. Large numbers of galaxy velocities obtained over a small area of sky to a faint limiting magnitude would help to construct a clearer picture of the medium scale (supercluster-sized) structure of the Universe.

In this thesis the basis for a method of obtaining radial velocities of faint galaxies from their objective prism spectra is described. Measurement techniques, both manual and computer -based, using digitised data from several measuring machines, are discussed. The parameters able to affect the velocity measurement are examined, and checks are made to compare velocities obtained from objective prism spectra with velocities of the same objects obtained from slit spectra. The method is shown to be easily applied to measurements of individual known galaxies, but quite difficult to apply to large numbers of objects using computer techniques. In particular the signal to noise ratio in galaxy spectra has a very important effect on automated velocity measurements.

elocity measurements. The application of the method to clusters of galaxies is demonstrated, and preliminary results presented for several Abell clusters. The application of the method to the general field is discussed, and the problems encountered with this application described. It is concluded that the technique described has great potential for both the study of clusters of galaxies, and if certain measurement problems can be overcome, for the study of the distribution of galaxies in large volumes of space.

http://hdl.handle.net/1842/30837

The University of Edinburgh

Annexe Thesis Digitisation Project 2018 Block 19

Radial velocities of faint galaxies from objective prism spectra

Thesis or Dissertation

Doctoral

PhD Doctor of Philosophy