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118 6. Faraday rotation in two extreme environments 0 20000 40000 60000 12 24 00 12 23 40 DECLINATION (J2000) 12 23 20 12 23 00 12 22 40 12 30 51 12 30 50 12 30 49 12 30 48 12 30 47 RIGHT ASCENSION (J2000) Figure 6.8: Left: Image of Burn law k for M 87 computed from weighted least-squares fits to the relation p(λ)= p(0)exp(−kλ 4 ) at the eight frequencies listed in Table 6.3. Right: Profiles of Burn law k along the jet direction, plotted against distance from the nucleus. The angular resolution is 0.4 arcsec FWHM. The Burn law k map for M 87 is shown in Fig. 6.8. At 0.4 arcsec resolution the overall k distribution has a mean of 9820 rad 2 m −4 , corresponding to a depolarization DP 6cm 3cm = 0.85. The mean observed k values for the two lobes are listed in Table 6.4. The highest depolarization occurs in patchy structures in the E (receding) lobe, consistent with the Laing-Garrington effect (Laing 1988; Garrington et al. 1988). These structures appear filamentary and are likely to be caused by steep (and therefore unresolved) RM gradients. Indeed, they are in the same areas as the highest absolute values of RM and∇RM (Fig. 6.7). In addition to low and constant RM, the jet also shows uniformly low k. The profile of 〈k〉 across the source (Fig. 6.8, right) is qualitatively similar to that observed in 0755+37, but more extreme: it increases monotonically from W to E across the core, peaks in the E lobe and then decreases at larger distances. Except in the region of the jet, no detailed correlation of depolarization with source morphology is apparent. Together with the absence of significant deviations fromλ 2 rotation, this again requires a Faraday rotating medium mostly external to the source. 6.3 Two-dimensional analysis: structure functions I used the RM structure function (Eq. 3.13) to quantify the two-dimensional fluctuations of Faraday rotation measure on scales larger than the observing beamwidth for 0755+37 and M 87. 118
6.3. Two-dimensional analysis: structure functions 119 0755+37 Figure 6.9: RM structure functions for the sub-regions of 0755+37 indicated in the panels at 4.0 and 1.3 arcsec FWHM. The horizontal bars represent the bin widths and the crosses the mean separation for data included in the bins. The red curves are the best fits, including the effects of the convolving beam. The error bars represent the rms variations for structure functions derived from multiple realizations of the indicated power spectrum on the observed grid. 119
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Alma Mater Studiorum Università de
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To Hypatia from Alexandria in Egypt
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Contents Abstract i 1 Physics of ra
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4.6.3 The outer scale of the magnet
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Abstract The existence of diffuse m
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2. Two-dimensional Monte Carlo simu
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Chapter 1 Physics of radio galaxies
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1.2. Non-thermal emission mechanism
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1.2. Non-thermal emission mechanism
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1.3. Radio galaxies 7 FR II sources
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1.3. Radio galaxies 9 (a) (b) Figur
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1.3. Radio galaxies 11 pressure, th
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Chapter 2 The X-ray environment of
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2.2. The thermal component 15 Figur
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2.3. Radio source - environment int
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2.3. Radio source - environment int
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Chapter 3 Magnetic fields in the ho
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3.1. Introduction 23 Figure 3.1: Ex
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3.1. Introduction 25 to the relativ
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3.2. Faraday Rotation 27 The RM can
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3.2. Faraday Rotation 29 Figure 3.4
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3.3. Depolarization 31 3.3 Depolari
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3.5. The magnetic field profile 33
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3.6. Tangled magnetic field 35 rad
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3.7. The magnetic field power spect
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Chapter 4 Structure of the magneto-
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4.1. The radio source 3C 449: gener
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4.3. The Faraday rotation in 3C 449
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4.3. The Faraday rotation in 3C 449
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4.4. Depolarization 51 Figure 4.4:
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4.4. Depolarization 53 1.25 arcsec
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4.5. Two dimensional analysis 55 sm
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4.5. Two dimensional analysis 57 Fi
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4.6. Three-dimensional analysis 59
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Page 83 and 84: 4.7. Summary and comparison with ot
Page 89 and 90: Chapter 5 Ordered magnetic fields a
Page 91 and 92: 5.1. The Sample 75 35 49 00 ROSAT P
Page 93 and 94: 5.1. The Sample 77 5.1.1 0206+35 02
Page 95 and 96: 5.2. Analysis of RM and depolarizat
Page 97 and 98: 5.3. Rotation measure images 81 IMA
Page 99 and 100: 5.3. Rotation measure images 83 cor
Page 101 and 102: 5.4. Depolarization 85 Therefore, a
Page 103 and 104: 5.5. Rotation measure structure fun
Page 105 and 106: 5.6. Rotation-measure bands from co
Page 111 and 112: 5.7. Rotation-measure bands from a
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Page 115 and 116: 5.8. Discussion 99 5.8 Discussion 5
Page 117 and 118: 5.8. Discussion 101 line−of−sig
Page 119 and 120: 5.8. Discussion 103 flat slopes. I
Page 121 and 122: 5.9. Conclusions and outstanding qu
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Page 125 and 126: Chapter 6 Faraday rotation in two e
Page 127 and 128: 6.2. Two-dimensional analysis: rota
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Page 137 and 138: 6.4. Preliminary conclusions 121 Ta
Page 139 and 140: 6.4. Preliminary conclusions 123
Page 141 and 142: Summary and conclusions The goal of
Page 143 and 144: 6.5. Summary 127 responsible for th
Page 145 and 146: 6.6. General conclusions 129 radio
Page 147 and 148: 6.7. Future prospects 131 and is th
Page 149: Appendix 133
Page 152 and 153: 136 Data reduction and imaging of l
Page 160 and 161: 144 BIBLIOGRAPHY Bîrzan, L., Raffe
Page 162 and 163: 146 BIBLIOGRAPHY Ensslin, T.A. & Go
Page 164 and 165: 148 BIBLIOGRAPHY Jeltema, T.E. & Pr
Page 166 and 167: 150 BIBLIOGRAPHY Owen, F.N., 1989,
Page 168 and 169: 152 BIBLIOGRAPHY 152
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Alma Mater Studiorum Universit`a degli Studi di Bologna ... - Inaf

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