L. H. Aller

Physics of Thermal Gaseous Nebulae (eBook, PDF)

Physical Processes in Gaseous Nebulae

• Format: PDF

Produktbeschreibung

Gaseous nebulae offer outstanding opportunities to atomic physicists, spectroscopists, plasma experts, and to observers and theoreticians alike for the study of attenuated ionized gases. These nebulae are often dusty, heated by radiation fields and by shocks. They are short-lived phenomena on the scale of a stellar lifetime, but their chemical compositions and internal kinematics may give important clues to advanced stages of stellar evolution. The material herein presented is based on lectures given at the University of Michigan, University of Queensland, University of California, Los Angeles, and in more abbreviated form at the Raman Institute, at the Scuola Internazionale di Trieste, and elsewhere. Much of it is derived origionally from the series "Physical Processes in Gaseous Nebulae" initiated at the Harvard College Observatory in the late 1930s. I have tried to emphasize the basic physics of the mechanisms involved and mention some of the uncertainties that underlie calculations of many basic parameters. Emphasis is placed on ionized plasmas with electron temperatures typically in the neighborhood of 10,OOOoK. Dust and other ingredients of the cold component of the interstellar medium are treated briefly from the point of view of their relation to hot plasmas of H II regions and planetaries. Chemical composition determinations for nebulae are discussed in some detail while the last section deals with interpretations of elemental abundances in the framework of stellar evolution and nucleogenesis. Gaseous nebulae offer some particularly engaging opportunities for studies of stellar evolution.

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Produktdetails

• Verlag: Springer Netherlands
• Seitenzahl: 350
• Erscheinungstermin: 6. Dezember 2012
• Englisch
• ISBN-13: 9789401096393
• Artikelnr.: 43981841

Inhaltsangabe

Preface.- 1: Types of Gaseous Nebulae.- Examples of Gaseous Nebulae.- HII Regions or Diffuse Nebulae.- Planetary Nebulae.- Supernova Remnants.- The 30 Doradus Nebular Complex.- Nonspatially Resolvable Objects, Galaxies and Stars.- Combination Variables and Other Exotic Objects.- A Concise List of References.- List of Illustrations.- 2: Spectra of Gaseous Nebulae.- 2A. The Primary Mechanism.- 2B. Collisionally-Excited Lines.- 2C. Permitted Lines in the Optical Region.- Some Suggested References.- List of Illustrations.- 3: Radiative Excitation, Ionization, Recombination, and Fluorescence.- 3A. Basic Relationships.- 3B. The Strömgren Sphere.- 3C. Free-Free Emission and BrehmsStrahlung.- 3D. Ionization Equation for Complex Atoms.- 3E. Dielectronic Recombination.- 3F. Collisional Ionization.- 3G. Charge Exchange.- 3H. Stellar Far Ultraviolet Radiation Fields.- 31. Line Excitation.- Problems.- Selected Bibliography.- List of Illustrations.- 4: Line and Continuous Spectra of Hydrogen and Helium.- 4A. Statistical Equilibrium, the Elementary Theory of the Balmer Decrement.- 4B. Improved Balmer Decrement Theory.- 4C. The Observed Balmer Decrement.- 4D. The Line and Continuous Spectrum of Hydrogen in the Radio-Frequency Region.- 4E. The Optical Continuum.- 4F. Hydrogen Plasmas at Moderately High Densities and Optical Thicknesses.- Problems.- References.- List of Illustrations.- 5: Collisionally Excited Lines and Plasma Diagnostics.- 5A (i). Collisional Excitation of Hydrogen Lines.- 5A (ii). Collisional Excitation of Lines of Heavier Elements.- 5A (iii). Transition Probabilities for Magnetic Dipole and Electric Quadrupole Transitions; a Quantum Mechanical Digression.- 5B (i). General Principles.- 5B (ii). Comments on Calculation of Collision Strengths.- 5C (i). "Low Density"Domain for p2 and p4 Configurations.- 5D (i). Collisionally-Excited Lines in the Near-Ultraviolet Region.- 5D (ii). Infrared Transitions.- 5D (iii). Ionic Concentrations for p3 Configurations.- 5E (i). Collisionally-Excited Lines as Tools for Plasma Diagnostics; Electron Temperatures.- 5E (ii). Collisionally-Excited Lines as Tools for Nebular Diagnostics; Electron Densities.- 5E (iii). Line Ratios That Depend on Both Temperature and Density.- 5F. Observational Checks on Accuracy of Theoretical Parameters.- Problems.- References.- List of Illustrations.- 6: Radiative Equilibrium of a Gaseous Nebula.- 6A. The Energy Balance of a Gaseous Nebula.- 6B. Persistence of a Maxwellian Velocity Distribution in a Photoionized Nebula.- Problem.- References.- List of Illustrations.- 7: Nebular Models.- 7A. Initial Assumptions.- 7B. Computational Procedures.- 7C. Dependence of Models on Input Parameters.- 7D. Some Complicating and Troublesome Factors for Nebular Model Constructions.- 7E. Time-Dependent Models.- 7F. Resonance Transitions and Transfer Problems.- 7G. Non-Radiative Excitation.- Problems.- References.- List of Illustrations.- 8: Dust and Related Phenomena in Gaseous Nebulae.- 8A. Extinction Effects Produced by Dust.- 8B. Dust and Infrared Spectra of Gaseous Nebulae.- 8C. Temperature and Energy Balance of the Dust.- 8D. Optical and Near UV Observations of Diffuse Nebulae.- 8E. Further Properties of Interstellar Dust Grains.- (1) Dust/Gas Ratio.- (2) Depletion of Refractory Elements in the Interstellar Medium.- (3) Linear Polarization.- (4) Variation of the Ratio R = AV/E(B-V).- (5) Are the Interstellar Media of Other Galaxies Similar to those of Our Own?.- References.- List of Illustrations.- 9: Shock Waves.- 9A. Introduction.- 9B. The Structure of Shocks.- 9C. Intricaciesand Complexities of Some Astrophysical Shock Phenomena.- 9D. Post-Shock Cooling Processes.- 9E. Radiative Transfer Effects.- 9F. Collisionless and Nonradiative Shocks.- 9G. Theoretical Models for Shock-Excited Nebulae.- 9H. Interpretation of Optical Spectra.- Problem.- References.- List of Illustrations.- 10: Diffuse Nebulae, Wind-Blown Shells and Planetaries.- 10A. Introduction.- 10B. Some Brief Comments on Molecular Clouds.- 10C. Relations Between H II Regions and Exciting Stars.- 10C1. Some Basic Considerations.- 10C2. The Orion Nebula.- 10C3. Sharpless 155 and a Nearby Cepheus Association.- 10D. Wind-Driven Shells and the Interstellar Medium.- 10D1. Some Theoretical Considerations.- 10D2. The Gum Nebula.- 10D3. 30 Doradus and NGC 604.- 10E. Planetary Nebulae.- 10E1. The Problem of Distances.- 10E2. Some Statistics of Planetary Nebulae.- 10E3. Structures and Internal Motions of Planetary Nebulae.- 10F. Bipolar Nebulae: Transition Objects or Young Planetaries.- References.- List of Illustrations.- 11: Chemical Compositions of Gaseous Nebulae.- 11A. Introduction.- 11B. Observational and Theoretical Problems of Composition Determination: Diffuse Nebulae.- 11C. Problems of Chemical Composition Determinations: Planetary Nebulae.- 11D. Examples of Abundance Determinations.- 11E. Compositions of Planetary Nebulae.- 11F. Planetary Nebular Compositions and Galactic Structure.- 11G. Abundance Determinations in H II Regions and Composition Gradients in Galaxies.- 11H. Abundance Gradients in the Disk of Our Galaxy.- References.- List of Illustrations.- 12: Nebular Compositions, Element Building, and Stellar Evolution.- 12A. Stellar Winds.- 12B. Late Stages of Stellar Evolution for Objects of Low-to-Intermediate Mass.- 12C. Origin of Planetary Nebulae; Some Theoretical Insightsand Observational Clues.- 12D. Carbon Stars and Their Relationship to Planetary Nebulae.- 12E. Comparison of Theory and Observations.- 12F. Notes on the Evolution of Very Massive Stars.- 12G. The Role of the Wolf-Rayet Stars.- 12H. Supernovae.- 12I. Principal Sources of Enrichment to the H II Regions.- 12J. H II Regions and the Chemical Evolution of Galaxies.- References.- List of Illustrations.- Appendix: Compilation of Transition Probabilities, Electron Excitation Rate Coefficients and Photoionization Cross sections.- 1. Indices.- 2. Methods.- 3. Accuracy.- 4. Transition Probabilities and Excitation Rate Coefficients.- References.- References to Individual Nebulae.- Index of Principal Symbols Used.

Rezensionen

`...Professor Aller has done the astronomical community a great service in writing this thoroughly excellent and interesting book. It is a mine of information and its a pleasure to read. It will undoubtedly become a classic book and is required reading for anyone who considers themselves to be an astrophysicist. I have rarely read a book I can commend so highly.'
Astrophysics and Space Science (1985)

`...Professor Aller has done the astronomical community a great service in writing this thoroughly excellent and interesting book. It is a mine of information and its a pleasure to read. It will undoubtedly become a classic book and is required reading for anyone who considers themselves to be an astrophysicist. I have rarely read a book I can commend so highly.'
Astrophysics and Space Science (1985)