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140 Data reduction and imaging of lobed radio galaxies .2.1 0206+35 The left panel of Fig. 11 shows the total intensity distribution over all of 0206+35 at 4.9 GHz, 1.2 arcsec resolution. At this resolution, both lobes are circular in cross-section and show sharp outer boundaries, particularly to the NW and SE of the source, plus some fainter diffuse emission to the N and S. If the orientation ofθ≈40 ◦ determined for the inner jets (Laing & Bridle, in preparation) also applies to the lobes, then they are presumably ellipsoidal with an axial ratio≈1. The figure also shows internal structure in both jets. NW jet has the brighter base, and both bends and brightens as it enters its lobe, after which its path meanders. The SE counter-jet appears to expand more rapidly initially, then also meanders as it enters its lobe. The right panel of Fig. 11 illustrates that the magnetic field configuration in both lobes is well ordered and basically circumferential, while near the central lines of the jets it is predominantly perpendicular to their axis, with evidence for parallel field at the jet edges. The southern edge of the source is strongly polarized with magnetic field tangential to the source boundary. .2.2 0755+37 Figs. 12(a) and (b) show the total intensity distribution over all of 0755+37 at two resolutions and frequencies. Fig. 12(a) at 1.4 GHz, 4.0 arcsec resolution, shows that the large scale structure consists of two lobes, again roughly circular in projection, with well-defined but not particularly sharp outer edges to the W and E, plus fainter diffuse emission to the N and S. The E lobe has a series of narrow rings and brightness steps in the region where the brighter jet appears to terminate. They are recessed from the eastern boundary of this lobe and some may be the edges of thin shells. The structure of the W lobe is unusual, containing some arc-like features. and other structure suggestive of a rapidly decollimating counter-jet W of the nucleus, as previously described by Bondi et al. (2000), with a “hole”, or deficit of emission in the region where the counter-jet might be expected to terminate. Although partially resolved out, all of these internal structures are confirmed by the higher resolution image at 4.9 GHz, 1.3-arcsec resolution (Fig. 12(b)). Figs. 12(c) and (d) show that the magnetic field in both lobes is exceptionally well organised, and mainly tangential to the lobe boundaries, at both the angular resolutions. At the lower resolution, the degree of linear polarization p≤0.6 over much of both lobes. Noteworthy is the excellent alignment between the field vectors and the ridges of high brightness gradient on both sides of the source. 140
.2. Images 141 0 2 4 6 8 10 12 14 37 48 30 15 00 (a) (c) DECLINATION (J2000) 47 45 30 15 00 46 45 30 15 00 0.0 0.5 1.0 1.5 2.0 2.5 p = 1 0.5 1.0 1.5 2.0 2.5 37 48 30 15 00 (b) (d) DECLINATION (J2000) 47 45 30 15 00 46 45 30 15 00 07 58 36 34 32 30 28 26 24 22 20 RIGHT ASCENSION (J2000) p = 1 07 58 36 34 32 30 28 26 24 22 20 RIGHT ASCENSION (J2000) Figure 12: images of 0755+37 at 4.0 arcsec (panels a and c) and 1.3 arcsec (panels b and d). (a) Total intensity at 1.4 GHz in mJy beam −1 . (b) Total intensity at 4.9 GHz in mJy beam −1 . Apparent B a vectors with lengths proportional to p 4.9 from the 3-frequency RM fits, superimposed on a false-colour display at 4.9 GHz of the intensity gradient (c) and the total intensity (d). The panels show identical areas. .2.3 M 84 The left panel of Fig. 13 shows the total intensity distribution over M 84 at 1.65 arcsec FWHM resolution. The source appears to be an intermediate case between lobed and tailed sources: the lobes, in particular the NE one, more closely resemble the inner plumes in FR I sources(3C 31, Laing et al. 2008), albeit on a much smaller linear scale (∼6 kpc) and somewhat rounder shape. On the other hand, the spectral gradients (Laing et al. in preparation) are more characteristic of lobed sources, with no hint of steepening outwards. Both jets expand rapidly and deflect within about 1 arcmin of the nucleus. They are surrounded by diffuse emission, at least in projection, everywhere except perhaps within a few arcsec of the nucleus. The North jet is brighter at its base and forms a plume-like structure without well-defined edges after deflecting though approximately 141
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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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4.7. Summary and comparison with ot
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Chapter 5 Ordered magnetic fields a
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5.1. The Sample 75 35 49 00 ROSAT P
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5.1. The Sample 77 5.1.1 0206+35 02
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5.2. Analysis of RM and depolarizat
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5.3. Rotation measure images 81 IMA
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5.3. Rotation measure images 83 cor
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5.4. Depolarization 85 Therefore, a
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5.5. Rotation measure structure fun
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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
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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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