X-ray luminous clusters of galaxies at z > 0.3

Abstract

This thesis presents optical CCD imaging taken as part of the follow-up programme to the Massive Cluster Survey, a ROSAT All-Sky Survey based cluster survey aiming to discover X-ray luminous galaxy clusters at redshifts above 0.3. A data-reduction pipeline is developed to process the V, R and I band imaging of 111 clusters observed with the University of Hawaii 2.2 metre telescope and 57 with the ESQ NTT. The galaxian population is examined and all clusters but one contain enough galaxies to account for the X-ray flux. The cluster red-sequence is used to constrain the star-formation epoch to high {z > 1.7) redshift and as a basis for photometric redshifts. The symmetry properties of the clusters are examined to probe merger activity, the cluster selection exhibiting no bias towards, or against, merging clusters. The BCG population is examined. The degree to which the BCG dominates the cluster galaxy population displays no trend with either redshift or cluster X-ray luminosity, indicative of considerable previous as well as ongoing evolution. A quarter of the BCG population show bluer colours than would be expected for an elliptical galaxy at the appropriate redshift, some with known line emission, proving that BCGs are not purely passively evolving galaxies. Multi-object spectroscopy of two clusters is used to confirm these as being massive. Colour-magnitude diagrams of spectroscopically selected galaxies are used to determine that the major source of error in the photometry to is the flux limit of the imaging not the techniques applied. The Veron-Cetty Veron AGN catalogue is cross-correlated with the Abell catalogue to reveal a sample of AGN in clusters which are found to be distributed within clusters as ordinary galaxies, making contamination to the observed X-ray flux a possibility. A search for gravitationally lensed galaxies reveals such objects in 23% of the clusters imaged. [brace not closed]