Intro; Supervisor's Foreword; Preface; Declaration; Acknowledgements; Contents; List of Figures; List of Tables; 1 Introduction; 1.1 Galaxy Clusters and Groups; 1.1.1 Cluster Dynamical State; 1.1.2 Diffuse Radio Emission in Galaxy Clusters; 1.1.3 Faraday Rotation in Galaxy Clusters; 1.1.4 Radio Halo Scaling Relationships; 1.1.5 Galaxy Groups; 1.2 Active Galactic Nuclei; 1.2.1 Radio Galaxies; 1.2.2 Quasars, Blazars, and Seyferts; 1.2.3 A Unified Model for AGN; 1.2.4 AGN and Feedback; 1.2.5 Particle Energetics; 1.2.6 Giant Radio Galaxies; 1.3 Astrophysical Processes; 1.3.1 Synchrotron Emission

1.3.2 Bremsstrahlung Radiation1.3.3 Faraday Rotation; 1.4 Structure of Thesis; References; 2 Techniques and Data Calibration; 2.1 Radio Interferometry; 2.1.1 Why Is Interferometry Needed; 2.1.2 Basic Interferometry; 2.2 Calibrating Interferometric Data; 2.2.1 Ionospheric Effects; 2.3 Imaging Techniques; 2.3.1 Multiscale Imaging; 2.3.2 W-Projection; 2.4 Rotation Measure Synthesis; 2.5 QU Fitting; 2.6 Instruments; 2.6.1 GMRT; 2.6.2 LOFAR; 2.6.3 VLA; 2.6.4 KAT-7; References; 3 A Newly-Discovered Radio Halo in Merging Cluster MACS J2243.3-093; 3.1 Introduction; 3.2 Observations and Data Reduction

3.2.1 KAT-73.2.2 GMRT; 3.3 Results; 3.3.1 MACS J2243.3-0935 at >1 GHz; 3.3.2 MACS J2243.3-0935 at <1 GHZ; 3.4 Discussion; 3.4.1 A Giant Radio Halo in MACS J2243.3-0935; 3.4.2 Possible Radio Relics in MACS J2243.3-0935; 3.5 Conclusion; References; 4 GMRT Observations of Three Highly Disturbed Clusters; 4.1 Introduction; 4.2 Observations and Data Reduction; 4.3 Results; 4.3.1 A07; 4.3.2 A1235; 4.3.3 A2055; 4.3.4 New Upper Limits; 4.4 Discussion; 4.5 Conclusion and Future Work; 4.5.1 Future Work; References; 5 LOFAR HBA Observations of NGC 6251; 5.1 Introduction

5.2 Observations and Data Reduction5.2.1 HBA Observations; 5.2.2 Archival Data; 5.3 Results; 5.3.1 Total Intensity Maps; 5.3.2 Internal Pressure; 5.3.3 Polarisation in NGC 6251; 5.4 Discussion; 5.5 Conclusions; References; 6 Conclusions; Index