Fundamentals of Radio Astronomy: Astrophysics

Description

As demonstrated by five Nobel Prizes in physics, radio astronomy has contributed greatly to our understanding of the Universe. Courses covering this subject are, therefore, very important in the education of the next generation of scientists who will continue to explore the Cosmos. This textbook, the second of two volumes, presents an extensive introduction to the astrophysical processes that are studied in radio astronomy. Suitable for undergraduate courses on radio astronomy, it discusses the physical phenomena that give rise to radio emissions, presenting examples of astronomical objects, and illustrating how the relevant physical parameters of astronomical sources can be obtained from radio observations. Unlike other radio astronomy textbooks, this book provides students with an understanding of the background and the underlying principles, with derivations available for most of the equations used in the textbook. Features: Presents a clear and concise discussion of the important astronomical concepts and physical processes that give rise to both radio continuum and radio spectral line emission Discusses radio emissions from a variety of astronomical sources and shows how the observed emissions can be used to derive the physical properties of these sources Includes numerous examples using actual data from the literature Cover Half Title Series Page Title Page Copyright Page Contents Preface Acknowledgments Chapter 1: Introductory Material 1.1 UNITS AND NOMENCLATURE 1.1.1 Issues with Units of Electricity and Magnetism 1.1.2 Astronomy Units 1.1.3 Nomenclature for Atomic Ionization States 1.2 RADIATION MEASURES 1.2.1 Luminosity 1.2.2 Flux 1.2.3 Flux Density 1.2.4 Intensity 1.2.5 Polarization 1.3 SKY COORDINATES 1.3.1 Equatorial Coordinate System 1.3.2 Galactic Coordinate System 1.4 DOPPLER EFFECT 1.4.1 Classical Doppler Effect 1.4.2 Relativistic Doppler Effect 1.5 COSMOLOGICAL REDSHIFT AND THE EXPANDING UNIVERSE 1.6 DISTANCE AND AGE CALCULATIONS QUESTIONS AND PROBLEMS Chapter 2: Propagation of Radiation 2.1 RADIATIVE TRANSFER 2.1.1 Absorption of Radiation 2.1.2 Emission of Radiation 2.1.3 General Radiative Transfer Equation 2.2 PROPAGATION IN AN IONIZED MEDIUM 2.2.1 Plasma Frequency 2.2.2 Dispersion Measure 2.2.3 Faraday Rotation QUESTIONS AND PROBLEMS Chapter 3: Continuum Emission Processes 3.1 RADIATION FROM ACCELERATED CHARGES 3.2 THERMAL RADIATION 3.2.1 Blackbody Radiation 3.2.2 Rayleigh-Jeans Approximation 3.2.3 Brightness Temperature 3.2.4 Thermal Bremsstrahlung Radiation (or Free-Free Emission) 3.3 NON-THERMAL RADIATION 3.3.1 Cyclotron Radiation 3.3.2 Synchrotron Radiation by a Single Relativistic Electron 3.3.3 Radiation by an Ensemble of Relativistic Electrons 3.3.4 Polarization of Synchrotron Radiation 3.3.5 Optical Depth Effects: Synchrotron Self-Absorption QUESTIONS AND PROBLEMS Chapter 4: Spectral Lines 4.1 EMISSION AND ABSORPTION LINES 4.1.1 Einstein Coefficients 4.1.1.1 Spontaneous Emission 4.1.1.2 Absorption 4.1.1.3 Stimulated Emission 4.1.1.4 Absorption Coefficient 4.1.1.5 Relations between the Einstein A and B Coefficients 4.1.2 Line Broadening 4.1.3 Spectral Line Radiative Transfer 4.1.4 Kirchhoff’s Rules for Spectroscopy 4.1.5 Collisional Transition Rates and Excitation Temperature 4.2 RADIO SPECTRAL LINES 4.2.1 21-cm Spectral Line of Atomic Hydrogen 4.2.2 Radio Recombination Spectral Lines 4.2.3 Molecular Rotational Spectral Lines QUESTIONS AND PROBLEMS Chapter 5: The Cold Interstellar Medium of the Milky Way 5.1 21-CM SPECTRAL LINE OF ATOMIC HYDROGEN 5.1.1 Observations of the 21-cm Line 5.1.2 Rotation Curve of the Galaxy 5.1.3 Distribution of HI in the Milky Way 5.1.4 Absorption Lines - Warm and Cold Gas 5.1.5 Magnetic Field 5.2 OBSERVATIONS OF THE ROTATIONAL LINES OF MOLECULES 5.2.1 Molecular Clouds 5.2.2 Distribution of Molecular Clouds in the Galaxy 5.2.3 Molecular Cloud Cores 5.2.4 Astrochemistry 5.3 OBSERVATIONS OF THE THERMAL EMISSION FROM DUST 5.3.1 Dust Extinction 5.3.2 Dust Emission 5.3.3 Global Distribution of Dust QUESTIONS AND PROBLEMS Chapter 6: HII Regions and Planetary Nebulae at Radio Wavelengths 6.1 HII REGIONS 6.1.1 Ionization Structure of HII Regions 6.1.2 The Temperature of HII Regions 6.1.3 Time Scales of HII Regions 6.2 RADIO EMISSION FROM HII REGIONS 6.2.1 Bremsstrahlung Emission from HII Regions 6.2.2 Radio Recombination Line Emission from HII Regions 6.2.3 Gas Density and Temperature from RRLs: Non-Equilibrium Effects 6.3 THE CLASSIFICATION AND EVOLUTION OF HII REGIONS 6.3.1 Classification of HII Regions 6.3.2 Evolution of HII Regions 6.4 PLANETARY NEBULAE QUESTIONS AND PROBLEMS Chapter 7: Radio Emission from Stellar Objects 7.1 SOLAR RADIO EMISSION 7.1.1 The Quiet Sun 7.1.2 Slowly Varying Component of the Sun 7.1.3 Radio Bursts 7.2 RADIO EMISSION FROM STARS 7.2.1 Thermal Radio Emission 7.2.1.1 Main Sequence Stars 7.2.1.2 Giant and Supergiant Stars 7.2.2 Winds from Asymptotic Giant Branch Stars 7.2.3 Flare Stars 7.3 YOUNG STARS 7.3.1 Proto-stellar Disks 7.3.2 Thermal Radio Jets 7.3.3 Molecular Outflows 7.4 RADIO PULSARS 7.4.1 Pulsar Mechanics 7.4.2 Pulsar Emission Mechanisms 7.4.3 Pulsar Searches 7.4.4 Binary Pulsars 7.4.5 Radio Pulsars as Probes of the Interstellar Medium 7.4.6 Supernova Remnants QUESTIONS AND PROBLEMS Chapter 8: Galaxies at Radio Wavelengths 8.1 21-CM HI OBSERVATIONS 8.1.1 HI Mass of Galaxies 8.1.2 Imaging HI in Galaxies 8.2 MOLECULAR GAS IN GALAXIES 8.2.1 Molecular Gas Mass 8.2.2 Imaging CO in Galaxies 8.2.3 Other Molecules in Galaxies 8.3 RADIO CONTINUUM EMISSION FROM GALAXIES 8.3.1 Dust Emission 8.3.2 Long Wavelength Radio Continuum Emission 8.4 DISTANT GALAXIES QUESTIONS AND PROBLEMS Chapter 9: Radio Galaxies and Quasars 9.1 BRIEF OVERVIEW OF ACTIVE GALACTIC NUCLEI 9.2 AGN MODEL 9.3 MORPHOLOGIES, SIZES, AND SPECTRA OF RADIO GALAXIES AND QUASARS 9.3.1 Synchrotron Spectrum from an Inhomogeneous Source 9.3.2 Free-free Absorption of Synchrotron Radiation 9.3.3 Inverse Compton Scattering and the Compton Limit 9.4 INFERRING PHYSICAL CONDITIONS IN AGN 9.4.1 Spectral Index Maps 9.4.2 Kinematic Studies 9.4.3 Magnetic Field Estimates 9.4.4 Electron Cooling Timescales and the Nature of Hot Spots in Jets 9.5 THE CENTER OF THE MILKY WAY QUESTIONS AND PROBLEMS Chapter 10: Cosmic Microwave Background 10.1 COSMOLOGICAL MODELS 10.2 BLACKBODY NATURE OF THE CMB 10.3 ANISOTROPIES IN THE CMB 10.4 COSMOLOGICAL PARAMETERS 10.5 CMB POLARIZATION QUESTIONS AND PROBLEMS Appendix A: Constants and Conversions Appendix B: Mathematica Code for Calculating Age of Universe and Distances for Given Redshift Appendix C: Complex-Valued Wave Functions Appendix D: Derivations of the Effects of Propagation of Radiation in Ionized Media D.1 BASIC EQUATIONS OF ELECTROMAGNETIC WAVES D.2 APPLICATIONS TO REAL MEDIA D.2.1 Dissipative Media D.2.2 The Plasma Frequency Equation D.2.3 Derivation of the Wave Velocity as a Function of Frequency and the Arrival Time of a Pulse D.3 DERIVATION OF THE ROTATION ANGLE OF POLARIZATION IN MAGNETIZED MEDIA Appendix E: Fourier Transform E.1 MATHEMATICAL DEFINITION E.2 EXAMPLE: FOURIER TRANSFORM OF A GAUSSIAN FUNCTION E.3 APPLICATION TO AN ACCELERATED CHARGE Index