Grigor A. Gurzadyan The Physics and Dynamics of Planetary Nebulae With 125 Figures, 14 Plates and 93 Tables Springer Contents 1. Global Concepts 1 1.1 The Shapes of Planetary Nebulae 1 1.2 The Structure of Nebulae 2 1.3 Luminosity and the Nuclei 5 1.4 The Optical Spectrum 6 1.5 The Spectrum of Nuclei 10 1.6 Stratification of Radiation: Observations 12 1.7 Excitation Class 13 1.8 Classification of the Shapes 16 1.9 Expansion of Nebulae 19 1.10 The Apparent Distribution of Planetary Nebulae 21 1.11 Planetary Nebulae in Other Galaxies 23 1.12 Designations, Catalogues, Surveys 25 2. The Origin of Emission Lines 27 2.1 The Nature of Nebular Emission 27 2.2 Rosseland's Theorem 29 2.3 Fluorescence: Zanstra's Theory 30; 2.4 Excitation of Forbidden Lines 32 2.5 Accumulation of Atoms in Metastable Levels 37 2.6 The Role of Electron Collisions 40 2.7 The Deactivation Effect 42 2.8 Stratification of Radiation: The Phenomenon 43 2.9 Emission Lines of Neutral Atoms 44 2.10 The Chemical Composition of Planetary Nebulae 45 2.11 Continuous Absorption and Recombination Coefficients .... 47 3. Emission Lines of Hydrogen and Helium 53 3.1 The Intensities of Balmer Lines of Hydrogen 53 3.2 The Role of Collisions 62 3.3 Comparison with Observations 63 3.4 The Balmer Decrement: Observations 64 3.5 The Decrement Diagram 67 3.6 Planetary Nebulae on the Decrement Diagram 69 X Contents 3.7 The Self-absorption Effect 70 3.8 Helium Emission Lines 71 3.9 Recombination Lines of Hell in the Ultraviolet 74 3.10 The Optical Depth of Nebulae at the Frequency of Helium Ionization 75 4. Ionization Equilibrium of Planetary Nebulae 79 4.1 Ionization of Nebulae 79 4.2 Ionization and Excitation by Electron Collisions 81 4.3 The Degree of Excitation 83 4.4 The Balmer Decrement for Collisions 84 4.5 The Ionization Structure of Planetary Nebulae 85 4.6 Thermal Equilibrium of Nebulae 86 4.7 Stratification of Radiation: Theory 94 4.8 Bowen Resonance Fluorescence 97 4.9 Excitation of the Resonance Level of Hydrogen by Electron Collisions 97 5. Temperature of Nebular Nuclei 99 5.1 Statement of the Problem 99 5.2 The Recombination Method: Zanstra's First Method 99 5.3 The "Nebulium Method": Zanstra's Second Method 103 5.4 The Hell/HI Method: Ambartsumian's Method 104 5.5 The Method of Fluxes: Seaton's Method 107 5.6 The [OIII]/[OII] Method 110 5.7 Temperatures of High Excitation Nebula Nuclei 112 5.8 Nuclei Temperatures of Low Excitation Nebulae 119 6. Electron Temperature. Electron Concentration 123 6.1 Statement of the Problem 123 6.2 The Electron Temperature 124 6.3 Cooling of the Inner Regions of a Nebula 129 6.4 The Temperature Gradient in a Nebula 130 6.5 The Temperature Gradient Within the Nebula: Observations 135 6.6 The Electron Concentration 137 6.7 The Masses of Planetary Nebulae 143 7. Planetary Nebulae in the Ultraviolet 147 7.1 The Structure of a Nebula's Spectra in the Ultraviolet 147 7.2 Resonance Lines in the Ultraviolet 149 7.3 The Macrostructure of the Spectra of Nebulae in the Ultraviolet 151 7.4 The Doublet 1550 CIV in Nebulae 155 7.5 Ultraviolet CIII Lines in Nebulae 158 7.6 The Ultraviolet Doublet 2 800 MgH 162 Contents XI 7.7 The Doublet 2 800 Mgll and the Physics of Gaseous Nebulae 164 7.8 Ionization of Magnesium in Nebulae 166 7.9 Determination of Dimensions of Stellar Envelopes 171 7.10 The Problem of Calcium Lines 172 7.11 The Short Wavelength Radiation of Nuclei 173 7.12 The Continuous Spectra of Nuclei in the Ultraviolet 176 7.13 Nuclei Temperatures According to Their Ultraviolet Spectra 177 7.14 Nuclei with Superhigh Temperatures 178 7.15 X-Rays from Planetary Nebulae 180 7.16 Correction for Interstellar Extinction of Emission in Ultraviolet Lines 182 7.17 Determination of Interstellar Extinction 183 8. Pseudoresonance Lines 187 8.1 Pseudoresonance Absorption Lines 187 8.2 Transition Probabilities of Pseudoresonance Lines 190 8.3 Possible Combinations Between Pseudoresonance and Forbidden Lines 192 8.4 The Optical Depth of a Nebula in Pseudoresonance Lines . 193 8.5 The Pseudoresonance Line 10 830 Hel in the Spectra of Gaseous Nebulae 195 8.6 Discovery of Pseudoresonance Lines 196 9. Continuous Radiation of Nebulae. Two-Photon Emission . 199 9.1 Statement of the Problem ': 199 9.2 The Theory of Two-Photon Emission of Hydrogen 200 9.3 The Role of Collisions 204 9.4 The Decay of La Photons 205 9.5 Theoretical Continuous Spectra of Nebulae in the Ultraviolet : 207 9.6 Theoretical Continuous Spectra of Nebulae in the Visual Region 211 9.7 Comparison with Observations 215 9.8 Orion-2: Two-Photon Emission of the Planetary Nebula IC 2 149 215 9.9 The Analogue of Zanstra's Formula for Two-Photon Emission 216 9.10 Two-Photon Emission of the Planetary Nebulae NGC 7 009 and NGC 7662 218 10. Infrared Radiation of Planetary Nebulae 223 10.1 The Structure of the Infrared Spectrum 223 10.2 Infrared Emission Lines of Nebulae 224 10.3 IRAS: Infrared Spectra of Planetary Nebulae 226 10.4 The Nature of Infrared Emission of Planetary Nebulae 229 XII Contents 10.5 Parameters of Dust Particles 230 10.6 Heating of Dust Particles in Nebulae 234 10.7 The Morphology of the Dust Component of a Nebula 235 10.8 Infrared Lines of [OIII] 235 10.9 The Temperature of Dust in Planetary Nebulae 238 10.10 The Survival of Dust Particles in Nebulae 238 10.11 Infrared Lines and the Temperatures of Nuclei 239 10.12 Evolution of Dust Particles in Planetary Nebulae 240 11. Radiative Equilibrium: Classical Theory 243 11.1 Statement of the Problem 243 11.2 The Lc Radiation Field 244 11.3 The La Radiation Field 248 11.4 The Radiation Field in an Expanding Nebula 251 11.5 Diffusion of La Radiation 254 11.6 The Relaxation Time 257 11.7 The Degree of Excitation of Resonance Level of Hydrogen . 258 12. Distances and Dimensions of Planetary Nebulae 261 12.1 Formulation of the Problem 261 12.2 Basic Methods '. 262 12.3 The Expansion Parallax Method 263 12.4 Spectral Distances 264 12.5 The Balmer Decrement Method 265 12.6 The Radio Flux Method: Individual and Statistical .266 12.7 The Interstellar Extinction Method 267 12.8 The Astrophysical Method 268 12.9 The Surface Gravity Method 268 12.10 The Helium Lines Method 269 12.11 The 21 cm HI Absorption Line Method 271 12.12 The Pseudoresonance Line Method 271 12.13 The Constant Mass Method 272 12.14 The Non-constant Mass Method 273 12.15 The Mass-Radius Correlation Method 275 12.16 The Radio Temperature-Radius Correlation 276 12.17 The Combined Statistical Method 276 12.18 Standard Distances 277 12.19 Catalogues of Distances of Planetary Nebulae 277 13. Double-Envelope Nebulae 279 13.1 Observational Aspects 279 13.2 Morphological Peculiarities 279 13.3 The Origin of the Second Envelope 280 13.4 The Similarity of Both Envelopes 281 13.5 Are Repeated Low Velocity Outbursts Possible? 282 Contents XIII 13.6 Physical Conditions in the Outer Envelope 282 13.7 The Mass of the Outer Envelope 282 13.8 The Ratio of Diameters of Both Envelopes 284 13.9 Haloes Around Nebulae 286 13.10 The Envelope Separation Concept 287 13.11 Evolution of Envelopes 289 13.12 The Frequency of Double Envelopes 290 13.13 Evolution of the Central Star 291 13.14 The Theory of Envelope Separation 293 13.15 The Structure of the Transition Zone 296 13.16 Separation of the Second Envelope 298 13.17 Three-Envelope Planetary Nebulae: Observations 302 13.18 Three-Envelope Nebulae: Their Origin 303 13.19 The Concept of Interacting Stellar Winds 307 13.20 The Syndrome of the Nebula NGC 7293 308 13.21 The Mystery of the Nebula NGC 6 543 309 14. Radio Emission of Planetary Nebulae 311 14.1 The Possibility of Radio Emission 311 14.2 The Expected Radio Spectrum of Nebulae 311 14.3 Radio Observations of Planetary Nebulae 313 14.4 Observed Radio Spectra of Planetary Nebulae 315 14.5 Radio Recombination Lines 317 14.6 The Planetary Nebula NGC 7027 319 14.7 Neutral Hydrogen in Planetary Nebulae ; 321 14.8 Interstellar Extinction from Radio Data 323 15. Anomalous Planetary Nebulae 327 15.1 Superdense Planetary Nebulae 327 15.2 M 1-2: The Densest Planetary Nebula 330 15.3 Superdense Nebulae on the Decrement Diagram 333 15.4 Nebulae Without Hydrogen: A New Class of Nebulae? 334 15.5 Nebulae with Contrasting Nuclei 340 15.6 Bipolar Outflow 342 15.7 Gaseous Envelopes with a Mixture of Dust 343 15.8 Planetary Nebulae with Gas-Dust Envelopes 346 15.9 A Method for Determining the Electron Temperature 351 15.10 Planetary Nebulae with Absorption Lines of Mgll and Mgl . 351 15.11 A "Cross-Like" Planetary Nebula 354 16. Dynamics of Planetary Nebulae 357 16.1 Light Pressure in Nebulae 357 16.2 Expansion of Nebulae: Theory 359 16.3 Expansion of Nebulae: Observations 365 16.4 Fast Winds from Central Stars : 367 XIV Contents 16.5 Shock Waves in Nebulae 369 16.6 Thermal Expansion: Voids in Nebulae. 371 16.7 Deceleration of Nebulae 373 16.8 The Hydrodynamics of Planetary Nebulae 376 16.9 Stability of the Forms of Gaseous Envelopes.