22.12.2013 Views

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

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

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

SHOW MORE
SHOW LESS

Create successful ePaper yourself

Turn your PDF publications into a flip-book with our unique Google optimized e-Paper software.

vi<br />

CONTENTS<br />

3.4.2 Real Space Analysis . . . . . . . . . . . . . . . . . . . . . . 56<br />

3.4.3 Fourier Space Analysis . . . . . . . . . . . . . . . . . . . . . 58<br />

3.4.4 Test the model and assess the influence <strong>of</strong> the window function 60<br />

3.5 Results . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 64<br />

3.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 67<br />

4 Pacman – A new RM Map Making Algorithm 71<br />

4.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 71<br />

4.2 The new Pacman algorithm . . . . . . . . . . . . . . . . . . . . . . . 73<br />

4.2.1 The Idea . . . . . . . . . . . . . . . . . . . . . . . . . . . . 73<br />

4.2.2 The Basic Algorithm . . . . . . . . . . . . . . . . . . . . . . 74<br />

4.2.3 Improving Quality . . . . . . . . . . . . . . . . . . . . . . . 78<br />

4.2.4 Restricting Gradients . . . . . . . . . . . . . . . . . . . . . . 78<br />

4.2.5 Topological Defects . . . . . . . . . . . . . . . . . . . . . . 78<br />

4.2.6 Spurious Points . . . . . . . . . . . . . . . . . . . . . . . . . 79<br />

4.2.7 Multi-Frequency Fits . . . . . . . . . . . . . . . . . . . . . . 79<br />

4.2.8 Additional Information . . . . . . . . . . . . . . . . . . . . . 80<br />

4.3 Testing the Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . 80<br />

4.4 Statistical Characterisation <strong>of</strong> Improved RM <strong>Maps</strong> . . . . . . . . . . 81<br />

4.4.1 Gradient Vector Product Statistic . . . . . . . . . . . . . . . 81<br />

4.4.2 Error Under or Over Estimation . . . . . . . . . . . . . . . . 82<br />

4.4.3 Magnetic Power Spectra . . . . . . . . . . . . . . . . . . . . 83<br />

4.5 Application to Data . . . . . . . . . . . . . . . . . . . . . . . . . . . 83<br />

4.5.1 Abell 2255E . . . . . . . . . . . . . . . . . . . . . . . . . . 83<br />

4.5.2 Hydra North . . . . . . . . . . . . . . . . . . . . . . . . . . 88<br />

4.5.3 The Quest for Hydra South . . . . . . . . . . . . . . . . . . . 94<br />

4.6 Lessons & Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . 97<br />

5 A Bayesian View on <strong>Faraday</strong> <strong>Rotation</strong> <strong>Maps</strong> 99<br />

5.1 Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 99<br />

5.2 Maximum Likelihood Analysis . . . . . . . . . . . . . . . . . . . . . 100<br />

5.2.1 The Covariance Matrix C RM . . . . . . . . . . . . . . . . . . 100<br />

5.2.2 Evaluation <strong>of</strong> the Likelihood Function . . . . . . . . . . . . . 103<br />

5.2.3 Binning and Rebinning . . . . . . . . . . . . . . . . . . . . . 103<br />

5.2.4 The Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . 104<br />

5.3 Testing the Algorithm . . . . . . . . . . . . . . . . . . . . . . . . . . 106<br />

5.4 Application to Hydra A . . . . . . . . . . . . . . . . . . . . . . . . . 108<br />

5.4.1 The Data ∆ . . . . . . . . . . . . . . . . . . . . . . . . . . . 108<br />

5.4.2 The Window Function . . . . . . . . . . . . . . . . . . . . . 109<br />

5.5 Results and Discussion . . . . . . . . . . . . . . . . . . . . . . . . . 111<br />

5.6 Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 115<br />

Conclusions 117<br />

Bibliography 119<br />

Acknowledgements 125

Hooray! Your file is uploaded and ready to be published.

Saved successfully!

Ooh no, something went wrong!