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THE POLARIZATION of RADIO GALAXIES -Its Structure at Low Frequencies

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THE POLARIZATION of RADIO GALAXIES -Its Structure at Low Frequencies STELLINGEN behorende bij het proefschrift THE POLARIZATION OF RADIO GALAXIES -its structure at low frequencies- 1. De structuur van de polarisatieverdelingen in uitgebreide extragalactische radiobronnen toont aan dat de veelgemaakte aanname van cilinder symmetrie voor de radiocomponenten onvolledig is (dit proefschrift). 2. Voor multispectrale vergelijkingen van radiokaarten van uitgebreide extragalactische stelsels ware het gewenst dat de Westerbork Synthese Radio Telescoop wordt uitgebreid met ontvangers bij een frequentie ergens tussen 610 MHz en 1400 MHz. 3. Het verloop van de spectrale index in zogenaamde edge-brightened double radio sources is slechts afhankelijk van de spectrale indices van de hot spots (dit proefschrift). 4. In de radiosterrenkunde blijft de theorie te ver achter bij de vele goede waarnemingen. 5. Om een goede astronoom te zijn moet men geloven dat het te bestuderen object de sleutel tot het heelal levert. 6. Bemande ruimtevaart moet waar mogelijk vermeden worden. 7. Sporters moeten zelf kunnen beslissen of zij een politiek omstreden evenement boycotten of niet. 8. Gelijktijdige pauze op alle Nederlandse astronomische instituten verhoogt de doelmatigheid. 9. De verwijzing private communication in wetenschappelijke literatuur is onacceptabel. 10. Het niet respecteren van Oost-Europese sportprestaties miskent het fenomeen topsport. 11. De huidige opzet van de dames tafeltennis competitie is nadelig voor het algehele dames spelniveau. W.J. Jagers Leiden, 2 december 1986 THE POLARIZATION OF RADIO GALAXIES its structure at low frequencies THE POLARIZATION OF RADIO GALAXIES its structure at low frequencies PROEFSCHRIFT ter verkrijging van de graad van Doctor in de Wiskunde en Natuurwetenschappen aan de Rijksuniversiteit te Leiden, op gezag van de Rector Magnificus Dr. J.J.M. Beenakker, hoogleraar in de Faculteit der Wiskunde en Natuurwetenschappen, volgens besluit van het College van Dekanen, te verdedigen op dinsdag 2 december1986 te klokke 14.15 uur door Willen) Joseph Jagers geboren te Rotterdam in 1957 Sterrewacht Leiden PROMOTIECOMMISSIE promotor: Prof. dr. H. van der Laan co-promotor: Dr. G.K. Miley referent: Dr. R.G. Strom leden: Prof. dr. W.B. Burton Prof. dr. H.J. Habing Prof. dr. W.W. Shane Prof. dr. P. Mazur aan Ingrid aan mijn ouders CONTENTS Chapter I Introduction and Summary 1 Interpretation of Polarization 11 Chapter II 0.6 GHz MAPPING OF EXTENDED RADIO GALAXIES I: 15 EDGE-BRIGHTENED DOUBLE SOURCES Summary 15 Introduction 15 Observations and Data Reduction 16 Results 21 Notes on the Sources 22 Chapter III 0.6 GHz MAPPING OF EXTENDED RADIO GALAXIES II: 49 EDGE-DARKENED DOUBLE SOURCES Summary 49 Introduction 49 Observations and Data Reduction 50 Results 52 Notes on the Sources 54 Chapter IV 0.6 GHz MAPPING OF EXTENDED RADIO GALAXIES III: 85 3C66B, NGC1265, 3C129, DA240, 3C236, 4C48.29, IC708 & IC711, 4CT51.29.1, 3C310, Abell2256, 3C4O2 and 3C465 Summary 85 Introduction 85 Observations and Data Reduction 86 Results 88 Notes on the Sources 90 Chapter V A MULTl-fHtgUüNCï HUUUmATlON STUUÏ UK In cooperation with J.P. Leahy and G.G. Pooley Astronomy and Astrophysics 156, 231 (1986) Summary 135 1. Introduction 135 2. Observations and Data Reduction 136 2.1 Westerbork 136 2.2 Cambridge - 2.7 GHz 136 2.3 Very Large Array 136 2.4 Multi-frequency comparison 137 3. Results 137 3.1 The core source 137 3.2 Spatial distributions 137 3.3 Statistical analysis of the polarization data 138 3.4 A foreground medium as well? 118 4. Discussion 148 4.1 The Faraday-active medium 148 4.2 The jets 149 4.3 The lobes (components B and E) 150 4.4 The large-scale structure 150 5. Conclusions 150 Appendix: Algorithms for rotation measure and 151 depolarization determinations A1. Rotation Measure 151 A2. Depolarization 151 Chapter VI LOW FREQUENCY POLARIZATION OBSERVATIONS OF THE RADIO 153 GALAXY 4C73.48. In cooperation with A.H.J.A. Dumoulin Summary 153 1. Introduction 153 2. Observations and Data Reduction 154 3. Results 157 3.1 Intensity and Polarization Maps 157 3.2 Magnetic Field and Thermal Electron 163 . Discussion 171 Chapter VII RADIO OBSERVATIONS OF THE GIANT QUASAR 4C31.47. 177 In cooperation with W.J.M, van Breugel, G.K. Miley, D.T. Schilizzi and R. Conway Astronomy and Astrophysics ^05, 278 (1982) Summary 177 I. Introduction 177 II. Observations and Data Reduction 177 III. Results 177 a. Total Intensity Distribution 177 b. Linear Polarization Distribution 177 c. Variability of the Core 179 d. Structure of the Core 181 IV. Discussion 181 Chapter VIII THE CLUSTER AROUND 3C13O. 183 Astronomy and Astrophysics 125, 172 (1983) Summary 183 I. Introduction 183 II. Observations and Data Reduction 183 III. Results 183 IV. Conclusion 185 Chapter IX THE RADIO STRUCTURE OF 3C13O INTERPRFTED WITH A 187 DYNAMICAL MODEL. In cooperation with M.H.K. de Grijp Astronomy and Astrophysics 1^3, 176 (1985) Summary 187 1. Introduction 187 2. Description of the model 187 2.1 The parent galaxy of 3C130 and its companions 187 2.2 The dynamics of the model 187 2.3 The radio observations 190 3. The results of the model fit 190 4. Discussion 190 5. Conclusions 191 Chapter X ONE-SIZED EJECTION IN THE PROTOTYPE TAILED RADIO 193 GALAXY 3C129? In cooperation with M.H.K. de Grijp Astronomy and Astrophysics 127, 235 (1983) Summary 193 I. Introduction 193 II. Observations and Data Reduction 193 III. Results 194 IV. Discussion 191 V. Conclusions Chapter XI 197 W. .1. JajU-rs 197 198 198 199 200 200 201 202 208 Chapter XII 0.6 GHz MAPPING OF EXTENDED RADIO GALAXIES IV: 211 SYSTEMATICS OF SPECTRAL INDEX DISTRIBUTIONS OF RADIO SOURCES AT LOW FREQUENCIES 1. Introduction 211 2. The spectral index distribution as a function 211 of morphology 2.1 Narrow edge-brightened double radio sources 211 2.2 Narrow edge-darkened double radio sources 215 2.3 Head-tail radio sources 215 2.4 Wide tailed radio sources 216 2.5 Conclusion 216 3. Systematics in the spectral index distributions 216 3.1 High-luminosity radio sources 216 3.2 Low-luminosity radio sources 219 4. Possible explanations for morphology dependence 220 of the observed spectral distribution 5. Conclusion 223 Chapter XIII 0.6 GHz MAPPING OF EXTENDED RADIO GALAXIES V: 225 SYSTEMATICS OF POLARIZATION DISTRIBUTIONS - EVIDENCE FOR EXCESS GAS ASSOCIATED WITH GIANT ELLIPTICAL GALAXIES 1. Introduction 225 1.1 General morphological conclusions from the 225 observations 1.2 Causes of depolarization 228 2. Where is the depolarizing material located? 230 2.1 Edge-brightened in the long wavelength 230 polarization structure: thermal material mixed with the radio lobes 2.2 Evidence for extensive gaseous halos 23*4 surrounding giant elliptical galaxies 2.3 Depolarization associated with regions of 248 optical line emission 2.4 Depolarization associated with gas in the 249 neighbourhood of the parent galaxy of the radio source 3. Concluding remarks 254 ALGEMENE SAMENVATTING 259 CURRICULUM VITAE 265 NAWOORD 267 CHAPTER I 1. Introduction and Summary Observing extended extragalaotic radio sources can be compared to unveiling the world's most exquisite paintings. These radio sources which are associated with galaxies and quasars are the largest and most beautiful astronomical objects in the universe. Much of our knovaedge about the physics of radio sources has been derived from morphological studies. During the past two decades there have been giant strides forward in these studies, mainly because of the improvements in the resolution, sensitivity and dynamic range of interferometric arrays. Through instruments such as the Westerbork SRT, the VLA, MERLIN and the Cambridge 5 km array as well as througt» very long baseline interferometry (VLBI) a huge body of data has been assembled. On the one hand using VLBI, resolutions of smaller than a milliarcsec have been attained (e.g. Preuss 1983. Barthel 1984), enabling investigation of the physical conditions in the nuclei of active galactic centres where radio sources are formed (Linfield 1982, Eilek 1982). On the other hand, lower resolution instruments (WSRT, Cambridge, VLA, MERLIN) have been used to study the properties of the large scale structures (e.g. Van Breugel 1980-b, Leahy 1984). Together they can give insight in the physical processes going on in the giant objects (e.g. Barthel et al. 1985, Leahv et al. 1986). During the last two decades a picture has emerged of extended radio sources as a manifestation of activity within the nuclei of their parent galaxies (e.g. Begelman et al. 1984). A rotating massive object, probably a l0 black hole of mass -10 -10 Mg in the nucleus, continuously accretes matter. It ejects a collimated flux of energy in two opposite directions along its angular momentum axis in a form of a recurrent spluttering of plasmons or a quasi-continuous beam of relativistic particles. Provided the nuclear activity is strong enough, prolonged enough, and/or stable enough in direction, an extended radio source is built up. The overall morphology of the extended lobes is determined by the degree of activity, as well as the amount of translational and/or rotational motion of the nuclear machine and the surrounding medium. There are several aspects of radio sources that are not yet understood. Here we shall refrain from comments on such basic questions as how the collimated beam is produced or as to the nature of the energy carrying fluid. This thesis will deal with observational data relevant to the nature and evolution of large scale radio emission and the medium where it is produced. Among radio sources a multiplicity of morphologies is visible. Miley (1980) categorized several classes of radio structure that are commonly seen, narrow edge-brightened double sources (Van Breugel and Jagers 1982), narrow edge-darkened double sources (Strom et al. 1983), wide double sources (Van Breugel 1980-a), narrow tailed sources (Rudnick and Burns 1981), wide tailed sources (Van Breugel 1980-c).
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