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Title: The most distant clusters
Author: Breukelen, Caroline van
ISNI:       0000 0001 3478 9917
Awarding Body: University of Oxford
Current Institution: University of Oxford
Date of Award: 2007
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The aim of this Thesis is to develop a new algorithm to detect high-redshift clusters of galaxies, to be used specifically with photometric redshifts derived from the latest near-infrared deep and wide-field imaging surveys. In Chapter 2 I describe the algorithm in detail, whose two main characteristics are: (i) the use of the complete photometric redshift probability distributions for all galaxies and (ii) the combination oftwo techniquesto select clusters, in order to minimise the detection of spurious sources. In Chapter 3 I present the first high-redshift optically/infrared selected cluster catalogue in the Subaru XMM-Newton Deep Field. The catalogue contains 13 clusters at 0.6 < z < 1.4 over 0.5 deg2 , which is in line with theoretical expectations. Chapter 4 describes the follow-up multi-object spectroscopy on six of the highest-redshift clusters. The clusters' reality is confirmed, and the previously derived photometric redshifts are compared with the spectroscopic redshifts. Our highest-redshift cluster candidate, CVB13 at z = 1.4, is discussed in detail in Chapter 5. The spectroscopic data reveal that instead of one massive cluster, the system comprises three lower-mass systems within b.z = 0.08, the most robust of which lying at z = 1.45. A cluster of similar mass is found at z = 1.28. I conclude that it is extremely difficult to obtain photometric redshifts accurate enough to distinguish between massive clusters and superimposed groups. Therefore it remains challenging to determine the cluster mass function at high redshift without spectroscopic follow-up. In Chapter 6 I investigate the X-ray and radio properties of four high-redshift clusters. I find that the two virialised clusters show diffuse X-ray emission but contain few, if any, X-ray point sources or radio galaxies. In contrast, the other two pre-virialisation clusters have a large X-ray and radio AGN population. It is likely that as the cluster virialises, AGN activity is extinguished, leaving the clusters quiescent.
Supervisor: Not available Sponsor: Not available
Qualification Name: Thesis (Ph.D.) Qualification Level: Doctoral
EThOS ID:  DOI: Not available