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Investigations of Faraday Rotation Maps of Extended Radio Sources ...

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Contents<br />

Abstract<br />

xi<br />

1 Introduction 1<br />

1.1 Magnetised Plasma . . . . . . . . . . . . . . . . . . . . . . . . . . . 2<br />

1.2 Observing Astrophysical Magnetic Fields . . . . . . . . . . . . . . . 5<br />

1.2.1 The Zeeman Effect . . . . . . . . . . . . . . . . . . . . . . . 5<br />

1.2.2 Polarisation <strong>of</strong> Optical Starlight . . . . . . . . . . . . . . . . 6<br />

1.2.3 Synchrotron Emission . . . . . . . . . . . . . . . . . . . . . 7<br />

1.2.4 <strong>Faraday</strong> <strong>Rotation</strong> . . . . . . . . . . . . . . . . . . . . . . . . 10<br />

1.3 The state <strong>of</strong> the Art - Cluster Magnetic Fields . . . . . . . . . . . . . 16<br />

1.3.1 <strong>Radio</strong> Haloes and Relics . . . . . . . . . . . . . . . . . . . . 16<br />

1.3.2 <strong>Rotation</strong> Measures . . . . . . . . . . . . . . . . . . . . . . . 18<br />

1.4 Some Statistical Tools . . . . . . . . . . . . . . . . . . . . . . . . . . 21<br />

1.4.1 Least-Squares & Error Weighting . . . . . . . . . . . . . . . 21<br />

1.4.2 Autocorrelation and Power Spectra . . . . . . . . . . . . . . 23<br />

1.4.3 Bayesian Statistics . . . . . . . . . . . . . . . . . . . . . . . 25<br />

1.4.4 Structure <strong>of</strong> the Thesis . . . . . . . . . . . . . . . . . . . . . 28<br />

2 Is the RM Source-Intrinsic or not? 29<br />

2.1 A Long Lasting Debate . . . . . . . . . . . . . . . . . . . . . . . . . 29<br />

2.2 The Argument Reconsidered . . . . . . . . . . . . . . . . . . . . . . 31<br />

2.3 Statistics Comes to Aid . . . . . . . . . . . . . . . . . . . . . . . . . 33<br />

2.4 Avoidable and Unavoidable Correlated Noise . . . . . . . . . . . . . 36<br />

2.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 37<br />

2.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 39<br />

3 Measuring Magnetic Field Power Spectra 41<br />

3.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 41<br />

3.2 The Philosophy . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 42<br />

3.3 The Method . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45<br />

3.3.1 Real Space Formulation . . . . . . . . . . . . . . . . . . . . 45<br />

3.3.2 Fourier Space Formulation . . . . . . . . . . . . . . . . . . . 48<br />

3.3.3 Testing the Model & Influences <strong>of</strong> Observational Artefacts . . 51<br />

3.3.4 Assessing the Influence <strong>of</strong> the Window Function . . . . . . . 53<br />

3.4 Application . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55<br />

3.4.1 3C75, 3C465 & Hydra A - the Data . . . . . . . . . . . . . . 55<br />

v

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