Durham E-Theses Imaging polarimetry of planetary and proto-planetary nebulae Bowlzer, S. L. How to cite: Bowlzer, S. L. (1997) Imaging polarimetry of planetary and proto-planetary nebulae, Durham theses, Durham University. Available at Durham E-Theses Online: http://etheses.dur.ac.uk/4718/ Use policy The full-text may be used and/or reproduced, and given to third parties in any format or medium, without prior permission or charge, for personal research or study, educational, or not-for-prot purposes provided that: • a full bibliographic reference is made to the original source • a link is made to the metadata record in Durham E-Theses • the full-text is not changed in any way The full-text must not be sold in any format or medium without the formal permission of the copyright holders. Please consult the full Durham E-Theses policy for further details. Academic Support Oce, Durham University, University Oce, Old Elvet, Durham DH1 3HP e-mail: [email protected] Tel: +44 0191 334 6107 http://etheses.dur.ac.uk Imaging Polarimetry of Planetary and Proto-Planetary Nebulae S. L. Bowlzer B.Sc. The copyright of this tliesis rests with die author. No quotation from it should be published witliout tlie written consent of the author and information derived from it should be ackiiowledced. A thesis submitted to the University of Durham for the degree of Doctor of Philosophy The copyright of this thesis rests with the author. No quotation from it should be published without his prior written consent and information derived from it should be acknowledged Department of Physics August 1997 !UL 199! Dedication / dedicate this doctoral thesis to the memory of my father. Together with my mum, his sacrificial help and support enabled me to finally complete the path that I started on such a long time ago. It is, therefore, with many mixed emotions that this work is finished. On the one hand, relief and joy to have, at last, brought this to a successful conclusion, but on the other, great sadness that my dad could not remain here to see this day, for it is as much to his credit as anyone. I wish that that I could tell him these thoughts face to face. One day, in a better world, I believe that I will ... Abstract Optical imaging polarimetry has been performed on a small sample of objects which are associated with that stage of stellar evolution occurring between the Asymptotic Giant Branch and full Planetary Nebula. Three such systems are considered, specif• ically, the young planetary nebulae Ml-16 and Mz3, and the protoplanetary nebula, IRAS 09371+1212 (the 'Frosty Leo' nebula). The work is based upon CCD polarimetry obtained with the Durham Imaging Polarimeter. Planetary nebulae are believed to form as a low to intermediate mass star evolves from the main sequence, through the mass-loss stages of the Red Giant Branch and Asymptotic Giant Branch, towards its final destiny as a White Dwarf. A brief review of the relevant aspects of post-main sequence stellar evolution is given as a basis for understanding the transitionary planetary nebula phase in relation to the character of the central star and its role in the creation of a nebula. The theory of light scattering from both homogeneous and core-mantle spherical dust grains (Mie theory) is discussed. The results of a series of scattering calculations, using the theory, for dust grains composed of those materials believed to be abundant in the atmospheres of late-type stars and planetary nebulae are presented. The levels of polar• ization and scattered intensities predicted in the scattering analysis have been applied in the interpretation of the polarimetric data for the three planetary nebulae. Constraints upon the nature of the dust component, the size distribution of the dust and the neb• ula geometry are suggested for each of the nebulae. The inferred character of the dust material is in good agreement with the classification of the nebulae using the two-colour diagram for the IRAS fluxes. Preface The body of work presented within this thesis deals mainly with the study of proto- planetary and planetary nebulae using the techniques of optical polarimetry. All the data, with the exception of IRAS 09371+1212, were recorded by the author using the Durham Imaging Polarimeter during observing time allocated to Dr. S. M. Scarrott at the Anglo-Australian Telescope, New South Wales and the South African Observatory in January/March 1994 and February 1997 respectively. Data reduction and analysis for all the objects was performed by the author, again with the exception of IRAS 09371+1212 for which the author carried out a fresh analysis and interpretation of data originally reduced and published by other members of the Durham Polarimetry Group (Scarrott & Scarrott, 1994, 1995). In the data analysis of Mz3, some use is made of the results of F-band optical polarimetry observations published in Scarrott h Scarrott (1995). None of the material presented within this thesis has been previously submitted for a degree at the University of Durham, or any other university. The data in this thesis were taken on telescope allocations made to Dr. S. M. Scarrott and Mr. S. Bowlzer and their permission must be obtained by anyone wishing to publish or use the results beyond this thesis. Contents 1 An Introduction to Planetary Nebulae 1 1.1 Introduction 1 1.2 Red Giants To Planetary Nebulae 5 1.2.1 Main Sequence Evolution 5 1.2.2 Post-Main Sequence Evolution 13 1.2.3 Mass loss on the Asymptotic Giant Branch 15 1.2.4 Post-AGB and the formation of planetary nebulae 16 1.3 Interacting Stellar Winds 21 1.4 Binary Star Interactions 26 1.5 Classification of Planetary Nebulae 28 1.6 Summary 33 2 Polarization and Planetary Nebulae 34 2.1 Introduction 34 2.2 Polarization via scattering 36 2.2.1 The polarization of light 36 2.2.2 Stokes parameters 38 2.2.3 The scattering of light by small particles 41 2.3 The origin of astrophysical solids 49 2.4 Dust in planetary nebulae , • 53 2.5 The scattering properties of dust grains 57 m 2.5.1 The size distribution of grains 58 2.5.2 An investigation into polarization by scattering from grains .... 60 3 Ml-16 71 3.1 Previous studies of M1-16 71 3.2 Observational details 88 3.3 Results 88 3.3.1 Intensity images 88 3.3.2 The effects of interstellar polarization 89 3.3.3 Polarization Maps 91 3.4 Discussion 100 3.4.1 The bipolar lobes of M 1-16 100 3.4.2 The geometry of M1-16 104 3.4.3 The nature of the dust grains in Ml-16 106 3.4.4 Evidence for a circumstellar disk? 116 3.5 Conclusions 116 4 The planetary nebula Mz 3 119 4.1 Previous studies of Mz 3 119 4.2 Observational details 124 4.3 Results 125 4.3.1 Intensity images 125 4.3.2 The effects of interstellar polarization 125 4.3.3 Polarization Maps 127 4.4 Discussion 137 4.4.1 The inner bipolar lobes 137 4.4.2 Evidence for a circumstellar disk? 137 4.4.3 The nature of the dust grains in Mz 3 138 4.5 Conclusions • 142 IV 5 The protoplanetary nebula IRAS 09371+1212 144 5.1 Previous studies of IRAS 09371+1212 144 5.2 Observational details 148 5.3 Results 149 5.3.1 Polarization maps 149 5.4 Discussion 169 5.4.1 The nature of the dust grains in IRAS 09371+1212 169 5.5 Conclusions 174 6 Summary and Conclusions 176 7 Mie scattering curves 181 Bibliography 209 List of Abbreviations 225 Acknowledgements 226 List of Figures 1.1 Hertzsprung-Russell diagram for pos<-Main sequence evolution 6 1.2 Hertzsprung-Russell diagram for the pos<-AGB stellar evolution phase 20 2.1 Polarization and scattered intensity from small Rayleigh particles 43 2.2 The geometry of scattering 45 3.1 Greyscale intensity contour image of M 1-16 in the \^-band 73 3.2 Greyscale intensity contour image of M 1-16 in Ha+N[II] 74 3.3 Total intensity profile of M 1-16 90 3.4 Intensity contour and polarization map of M 1-16 in the K-band 92 3.5 Intensity contour and polarization map of M 1-16 in Ha 94 3.6 Intensity contour and polarization map of M 1-16 in the V^-band (higher resolution) 96 3.7 Intensity contour and polarized intensity map of M 1-16 in the V-hund 97 3.8 Linear polarization trace for M 1-16 in the t^-band 98 3.9 Linear polarization trace for M 1-16 in the V-band 99 3.10 Profile of linear polarization (corrected for ISP) for M 1-16 in the ^/-band 101 3.11 Profile of polarized intensity (corrected for IS?) for M 1-16 in the V'-band 102 3.12 Schematic diagram of a simplified scattering geometry 106 3.13 Schematic diagram of a possible geometry for M 1-16 118 4.1 Greyscale intensity image of Mz 3 in Ha 120 4.2 Comparative images of Mz 3 in Ha and the V-band 126 4.3 Intensity contour and polarization map of Mz 3 in Ha 128 4.4 Greyscale intensity contour and polarised intensity contour (corrected for ISP) image of Mz 3 in Ha 129 4.5 Linear polarization trace (corrected for ISP) for Mz 3 131 4.6 Linear polarization trace (corrected for ISP) for Mz 3 132 VI 4.7 Trace of polarized intensity (corrected for ISP) for Mz 3 134 4.8 Trace of polarized intensity (corrected for ISP) for Mz3 135 4.9 Greyscale polarization image of Mz 3 in Ha (corrected for ISP) 136 5.1 Greyscale intensity contour and polarization map of IRAS 09371-1-1212 in the B- band 152 5.2 Greyscale intensity contour and polarization map of IRAS 0937H-1212 in the V- band 153 5.3 Greyscale intensity contour and polarization map of IRAS 09371-1-1212 in the R- band 154 5.4 Greyscale intensity contour and polarization map of IRAS09371-1-1212 in the I- band 155 5.5 Trace of intensity for IRAS 09371-1-1212 in the 5-band 157 5.6 Trace of polarization for IRAS 09371-1-1212 in the B-band 158 5.7 Trace of polarized