Clusters of galaxies

Thesis

The observations on which this thesis are based are of three types:

i) Spectroscopy of southern galaxies from which redshifts have been determined. These redshifts have enabled the calculation of velocity dispersions of the galaxies in five clusters of galaxies: Klemola 44, Sersic 40/6, 2354-35, A496 and the Pavo Group. Redshifts of galaxies in several other southern clusters have also been obtained.

ii) Photographic Photometry using digitised two-dimensional micro-densitometer scans of IIIaJ Schmidt plates of two southern clusters of galaxies: K44 and Sersic 40/6. Similar photometry of two other clusters, A1146 and 2354-35, is also available. Magnitudes in the B-band to a limiting isophote of 27mag/o" are obtained for all galaxies to a limiting magnitude of ~20 within a ~2Mpc (H_o = 50 km s^-1 Mpc^-1) square around the cluster. Methods of distinguishing stars from galaxies are discussed.

iii) Photoelectric photometry through several circular apertures of 21 bright southern galaxies, using the B, V, R and I bands. As well as providing catalogue data for southern galaxies, these readings supply magnitude zero-points for the photographic photometry of clusters.

The results are discussed in the light of current theories of the morphology, formation and evolution of clusters of galaxies. The X-ray flux from clusters of galaxies is found to be consistent with emission by bremsstrahlung from a hot intracluster gas. Four of the clusters: Klemola 44, 2354-35, A1146 and Sersic 40/6 contain cD galaxies. These galaxies increase in ellipticity with radius and are aligned with their clusters (except A1146); such properties are predicted if cD galaxies evolve by accretion of other galaxies. It is suggested that Klemola 44 may be undergoing a phase of rapid core evolution, leading to the accretion of the core by the cD galaxy. The cluster 2354-35 may have already passed through this evolutionary stage.

Authors: Green, M

• Peer review status: Peer reviewed
• Type of award: DPhil
• Level of award: Doctoral
• Awarding institution: University of Oxford