Galactic and Extragalactic Radio Astronomy

Galactic and Extragalactic Radio Astronomy is a fundamental text for graduate students and professional astronomers and covers all aspects of radio astronomy beyond the solar system. Each chapter is written by a renowned expert in the field and contains a review of a particular area of radio astronomy and presents the latest observations and interpretations as well as an extensive view of the literature (as of 1988). Topics covered include: galactic continuum emission, HII regions, the diffuse interstellar medium, interstellar molecules, astronomical masers, neutral hydrogen, the galactic center, radio stars, supernova remnants, pulsars, extragalactic hydrogen, radio galaxies and quasars, the microwave background, and cosmological radio sources.

Contenu

1. Galactic Nonthermal Continuum Emission.- 1.1 Introduction.- 1.1.1 Historical Preface.- 1.1.2 Early Surveys of Galactic Radio Emission.- a. Angular Distribution of the Cosmic Radio Waves.- b. Spectral Distribution of the Cosmic Radio Waves.- c. The Situation Circa-1956.- 1.2 Physical Processes.- 1.2.1 Synchrotron Radiation.- a. Single Particle Emission.- b. Radiation from an Ensemble of Particles.- c. Influence of the Medium.- 1.2.2 The Faraday Effect.- 1.3 Total Intensity Observations of the Galactic Radio Continuum.- 1.3.1 The Medium-Resolution Surveys.- 1.3.2 High-Resolution Surveys of the Galactic Plane.- 1.3.3 The Galactic Loops and Spurs.- 1.3.4 The Nonthermal Radiation and Galactic Structure.- 1.3.5 Galactic Radio Halo?.- 1.4 The Spectrum of the Nonthermal Emission.- 1.4.1 The Galactic Spectrum Above 10 MHz.- 1.4.2 The Very-Low-Frequency Spectrum.- 1.4.3 The Energy Spectrum of Cosmic-Ray Electrons.- 1.5 Linear Polarization of the Nonthermal Emission.- 1.5.1 Surveys of Linear Polarization of the Galactic Emission.- 1.5.2 Implications for the Local Magnetic Field.- 1.5.3 Magnetic Fields in the Galactic Loops.- 1.5.4 Rotation Measure Data and the Galactic Magnetic Field.- 1.6 The Galactic Nonthermal Radiation in Perspective.- Recommended Reading.- References.- 2. HII Regions and Radio Recombination Lines.- 2.1 Ionized Interstellar Hydrogen.- 2.1.1 Emission Nebulae.- 2.1.2 Diffuse Thermal Background.- 2.2 Radiation Transfer.- 2.3 Continuum Thermal Emission (Bremsstrahlung).- 2.3.1 Absorption and Emission Coefficients.- 2.3.2 Transfer Equation for Continuum Radiation.- 2.3.3 Low-Frequency Radiation from HII Regions.- 2.3.4 High-Frequency Radiation from HII Regions.- 2.3.5 Integrated Observations of HII Regions.- 2.3.6 Reality and the "Homogeneous Nebula" Approximation.- 2.3.7 Continuum Observations of HII Regions.- 2.3.8 Thermal Emission from Dust.- 2.4 Basic Theory of Radio Recombination Lines.- 2.4.1 Line Frequencies.- 2.4.2 Shape Function.- 2.4.3 Absorption and Emission Coefficients.- 2.4.4 Transfer Equation for Line Radiation.- 2.5 Refinements to the Transfer Equations.- 2.5.1 Local Thermodynamic Equilibrium.- 2.5.2 Departures from LTE.- 2.5.3 Turbulence Broadening.- 2.5.4 Pressure Broadening.- 2.6 Single-Dish Observations of Radio Recombination Lines from HII Regions.- 2.6.1 Early Observations of Integrated Line Intensities.- 2.6.2 Non-LTE Density-Gradient Models.- 2.6.3 Clumped Models.- 2.6.4 Comparison of the Density-Gradient and Clumped Models.- 2.6.5 Empirical Determinations of Electron Temperature.- 2.7 Exploration of the Milky Way by Radio Recombination Lines.- 2.7.1 Galactic Distribution of HII Regions.- 2.7.2 Galactocentric Variations of Electron Temperatures.- 2.7.3 Abundance Ratio of Helium to Hydrogen.- 2.7.4 The Diffuse Component.- 2.8 Radio Observations of HII Regions with High Angular Resolution.- 2.8.1 Continuum Observations.- 2.8.2 Recombination-Line Observations.- 2.9 Other Aspects of Radio Recombination Lines.- 2.9.1 Low Frequencies.- 2.9.2 Zeeman Effect.- 2.9.3 The Sun.- 2.9.4 Planetary Nebulae.- 2.9.5 Dark Clouds.- 2.9.6 Galaxies and Quasars.- Recommended Reading.- References.- 3. Neutral Hydrogen and the Diffuse Interstellar Medium.- 3.1 Introduction: Fundamentals.- 3.1.1 Radiative Transfer and Excitation of the HI Line.- 3.1.2 Observations of the Diffuse Medium.- a. Brief Review of the Four Phases: CNM, WNM, WIM, HIM.- b. Galactic Distribution of HI.- 3.1.3 Interstellar Pressure.- a.Excitation of CI Fine Structure.- b. Excitation of the CII Fine-Structure Lines.- c. Pressure of the WIM.- 3.1.4 Theory of the Kinetic Temperature of Diffuse Interstellar Gas.- a. Cooling Processes.- b. Heating Processes.- c. The Equilibrium Temperature.- d. Is Statistical Equilibrium Always Obtained?.- 3.1.5 Elements of Interstellar Gas Dynamics.- a. Static Equilibrium: The z-Structure in the Galaxy.- b. Static Equilibrium: A Uniform Spherical Magnetized Cloud.- c. Transient Features: Shocks.- 3.1.6 Two Famous Models of the Interstellar Medium.- 3.2 Structure of the Diffuse Interstellar Medium: HI Emission.- 3.2.1 Low-Velocity Gas.- a. Shells.- b. Filaments.- c. Major HI Concentrations Around Dark Clouds and Newly Formed Stars.- d. Shapes of HI Clouds.- e. Structure of HI Clouds.- 3.2.2 Intermediate-Velocity Gas.- 3.2.3 Supersheils and "Worms".- 3.3 Temperature and Ionization of the Diffuse Interstellar Medium.- 3.3.1 HI Absorption: Techniques, Data, and Analysis.- a. Techniques and Data.- b. Derived Spin Temperature: Definition and Limitations.- 3.3 2 Temperature of Warm HI.- 3.3.3 Temperature of the Cold HI (CNM).- a. Classical Absorption Studies: The T-? Relation.- b. Statistics of Clouds.- 3.3.4 Temperature Structure of HI Clouds.- a. Temperature Structure and the T-? Relation.- b. Physical Implications.- 3.3.5 Ionization of the Diffuse Interstellar Medium.- a. Observations.- b. Ionization Within Diffuse Clouds.- c. Where Do the Electrons Reside?.- d. The Energy Source for the WIM.- 3.3.6 Filling Factors of the WIM, WNM, and CNM.- 3.4 Interstellar Magnetic Fields.- 3.4.1 Methods of Measurement.- a. B?: Linear Polarization of Starlight.- b. B?: Linear Polarization of Synchrotron Radiation.- c. B?: Linear Polarization of Radio-Wavelength Spectral Lines.- d. B?: Faraday Rotation.- e. B?: Zeeman Splitting.- f. Faraday Rotation Versus Zeeman Splitting.- 3.4.2 Fields in External Galaxies.- 3.4.3 The Galactic Field on Scales Above 100 pc.- a. The Field Strength.- b. The Field Direction.- 3.4.4 The Galactic Field on Scales of 100 pc and Below.- 3.5 Summary.- Recommended Reading.- References.- 4. Molecules as Probes of the Interstellar Medium MID of Star Formation.- 4.1 Introduction.- 4.1.1 Historical Perspective.- 4.1.2 The Central Role of Molecular Spectroscopy.- 4.2 The Large-Scale Morphology of the ISM.- 4.2.1 The Physical Regimes of the ISM.- a. "Coronal" Gas.- b. Intercloud Gas.- c. Diffuse Interstellar Clouds.- d. Cold Dark Clouds.- e. Globules.- f. Giant Molecular Clouds.- g. Hot Molecular Cores in GMCs.- 4.2.2 The Morphology of Dense Molecular Clouds.- 4.2.3 GMCs and Spiral Arms.- 4.3 The Nature of Star-Forming Regions.- 4.3.1 Small Star-Forming Cores in SMCs and GMCs.- 4.3.2 Massive Star-Forming Cores in GMCs.- 4.3.3 Large-Scale Relationships of Star-Forming Regions.- a. Low-Mass-Star-Forming Regions.- b. Massive-Star-Forming Regions.- 4.3.4 Intermediate-Scale Structure: Velocity Outflows and Disks.- 4.3.5 Magnetic Fields.- 4.3.6 Small-Scale Structure of Star-Forming Regions.- a. The Orion Molecular Core.- b. Other Star-Forming Cores.- 4.3.7 A Summary of Star Formation Morphology.- 4.4 The Stability of Molecular Clouds and Cores.- 4.4.1 Star Formation Rates and the Stability of Molecular Clouds.- 4.4.2 Global Relations Between (n, L, ?v) for Molecular Clouds.- 4.4.3 Rotation.- 4.4.4 Magnetic Fields.- 4.4.5 Stellar Winds.- 4.4.6 "Gravito-Turbulence" or "Star Cloud Turbulence".- 4.5 The Formation of Stars.- 4.5.1 Low-Mass Stars from Low-Mass Cores.- 4.5.2 Formation of Massive Stars from Massive Cores.- a. A Summary of Observational Constraints.- b. Massive-Star Formation: Enhanced Accretion plus Shocks.- 4.5.3 A Stochastic Picture of Star Formation.- 4.6 Future Prospects.-…