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72 4. The magneto-ionic medium around 3C 449 IMAGE: RM_1.25_2000_SUBIM.FITS IMAGE: SUBIM_1.25.FITS ;200 ;150 ;100 RAD/M/M ;200 ;150 ;100 RAD/M/M Obs Syn IMAGE: RM_5.5_2000_SUBIM.FITS IMAGE: SUBIM_5.5.FITS ;200 ;150 ;100 RAD/M/M ;200 ;150 ;100 RAD/M/M Obs Syn Figure 4.13: Comparison of observed and representative synthetic distribution of Faraday RM at 1.25 arcsec and 5.5 arcsec. The synthetic images have been produced for the best-fitting model withΛ max =65 kpc. The colour scale is the same for all displays. 72
Chapter 5 Ordered magnetic fields around radio galaxies: evidence for interaction with the environment † M ost of the RM images of radio galaxies published so far show patchy structures with no clear preferred direction, consistent with isotropic foreground fluctuations over a range of linear scales ranging from tens of kpc to< ∼ 100 pc (e.g. 3C 449, Chapter 4; see also Govoni et al. 2006; Guidetti et al. 2008; Laing et al. 2008; Kuchar & Enßlin 2009; Bonafede et al. 2010), Numerical modelling has demonstrated that this type of complex RM structure can be accurately reproduced if the magnetic field is randomly variable with fluctuations on a wide range of spatial scales, and is spread throughout the whole group or cluster environment (Chapter 4; see also Murgia et al. 2004; Govoni et al. 2006; Guidetti et al. 2008; Laing et al. 2008; Bonafede et al. 2010). These authors used forward modelling, together with estimators of the spatial statistics of the RM distributions (structure and autocorrelation functions or a multi-scale statistic) to estimate the field strength, its relation to the gas density and its power spectrum. The technique of Bayesian maximum likelihood has also been used for this purpose (Enßlin & Vogt 2005; Kuchar & Enßlin 2009). In order to derive the three-dimensional magnetic field power spectrum, all of these authors had to assume statistical isotropy for the field, since only the component of the magnetic field along the line-of-sight contributes to the observed RM. This assumption is consistent with the absence of a preferred direction in most of the RM images. In contrast, the present Chapter reports on anisotropic RM structures, observed in lobed radio galaxies located in different environments, ranging from a small group to one of the richest clusters † Guidetti et al. 2011, MNRAS, in press 73
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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
Page 37 and 38: Chapter 3 Magnetic fields in the ho
Page 39 and 40: 3.1. Introduction 23 Figure 3.1: Ex
Page 41 and 42: 3.1. Introduction 25 to the relativ
Page 43 and 44: 3.2. Faraday Rotation 27 The RM can
Page 45 and 46: 3.2. Faraday Rotation 29 Figure 3.4
Page 47 and 48: 3.3. Depolarization 31 3.3 Depolari
Page 49 and 50: 3.5. The magnetic field profile 33
Page 51 and 52: 3.6. Tangled magnetic field 35 rad
Page 53 and 54: 3.7. The magnetic field power spect
Page 59 and 60: Chapter 4 Structure of the magneto-
Page 61 and 62: 4.1. The radio source 3C 449: gener
Page 63 and 64: 4.3. The Faraday rotation in 3C 449
Page 65 and 66: 4.3. The Faraday rotation in 3C 449
Page 67 and 68: 4.4. Depolarization 51 Figure 4.4:
Page 69 and 70: 4.4. Depolarization 53 1.25 arcsec
Page 71 and 72: 4.5. Two dimensional analysis 55 sm
Page 73 and 74: 4.5. Two dimensional analysis 57 Fi
Page 75 and 76: 4.6. Three-dimensional analysis 59
Page 83 and 84: 4.7. Summary and comparison with ot
Page 85 and 86: 4.7. Summary and comparison with ot
Page 87: 4.7. Summary and comparison with ot
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
Page 113 and 114: 5.7. Rotation-measure bands from a
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
Page 123 and 124: 5.9. Conclusions and outstanding qu
Page 125 and 126: Chapter 6 Faraday rotation in two e
Page 127 and 128: 6.2. Two-dimensional analysis: rota
Page 135 and 136: 6.3. Two-dimensional analysis: stru
Page 137 and 138: 6.4. Preliminary conclusions 121 Ta
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6.4. Preliminary conclusions 123
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Summary and conclusions The goal of
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6.5. Summary 127 responsible for th
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6.6. General conclusions 129 radio
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6.7. Future prospects 131 and is th
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Appendix 133
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136 Data reduction and imaging of l
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144 BIBLIOGRAPHY Bîrzan, L., Raffe
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146 BIBLIOGRAPHY Ensslin, T.A. & Go
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148 BIBLIOGRAPHY Jeltema, T.E. & Pr
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150 BIBLIOGRAPHY Owen, F.N., 1989,
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152 BIBLIOGRAPHY 152
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