Table Of ContentFundamentals of Radio
Astronomy
Astrophysics
Series in Astronomy and Astrophysics
The Series in Astronomy and Astrophysics includes books on all aspects of theoretical and experimental
astronomy and astrophysics. Books in the series range in level from textbooks and handbooks to
more advanced expositions of current research.
Series Editors:
M Birkinshaw, University of Bristol, UK
J Silk, University of Oxford, UK
G Fuller, University of Manchester, UK
Recent books in the series
Dark Sky, Dark Matter
J M Overduin and P S Wesson
Dust in the Galactic Environment, 2nd Edition
D C B Whittet
The Physics of Interstellar Dust
E Krügel
Very High Energy Gamma-Ray Astronomy
T C Weekes
Numerical Methods in Astrophysics: An Introduction
P Bodenheimer, G P Laughlin, M Rózyczka, H W Yorke
An Introduction to the Physics of Interstellar Dust
Endrik Krugel
Astrobiology: An Introduction
Alan Longstaff
Fundamentals of Radio Astronomy: Observational Methods
Jonathan M Marr, Ronald L Snell, and Stanley E Kurtz
Stellar Explosions: Hydrodynamics and Nucleosynthesis
Jordi José
Cosmology for Physicists
David Lyth
Cosmology
Nicola Vittorio
Cosmology and the Early Universe
Pasquale Di Bari
Fundamentals of Radio Astronomy: Astrophysics
Ronald L. Snell, Stanley E. Kurtz, and Jonathan M. Marr
Fundamentals of Radio
Astronomy
Astrophysics
Ronald L. Snell
University of Massachusetts, Amherst, Massachusetts, USA
Stanley E. Kurtz
National Autonomous University of Mexico, Morelia, Michoacan, Mexico
Jonathan M. Marr
Union College, Schenectady, New York, USA
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Names:Snell,RonaldLee,author.|Kurtz,Stanley,author.|Marr,JonathanM.,author.
Title:Fundamentalsofradioastronomy:astrophysics/RonaldL.Snell,StanleyE.Kurtz,
JonathanM.Marr.
Othertitles:Seriesinastronomyandastrophysics.
Description:BocaRaton,FL:CRCPress,Taylor&FrancisGroup,[2019]|
Series:Seriesinastronomyandastrophysics|Includesbibliographicalreferencesandindex.
Identifiers:LCCN2018051118|ISBN9781498725774(hbk;alk.paper)|
ISBN1498725775(hbk;alk.paper)
Subjects:LCSH:Radioastronomy.|Astrophysics.
Classification:LCCQB476.5.S642019|DDC522/.682--dc23
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Contents
Preface xi
Acknowledgments xiii
Chapter 1(cid:2) Introductory Material 1
1.1 UNITS AND NOMENCLATURE 2
1.1.1 Issues with Units of Electricity and Magnetism 2
1.1.2 Astronomy Units 4
1.1.3 Nomenclature for Atomic Ionization States 5
1.2 RADIATION MEASURES 5
1.2.1 Luminosity 5
1.2.2 Flux 5
1.2.3 Flux Density 6
1.2.4 Intensity 8
1.2.5 Polarization 10
1.3 SKY COORDINATES 13
1.3.1 Equatorial Coordinate System 13
1.3.2 Galactic Coordinate System 15
1.4 DOPPLER EFFECT 15
1.4.1 Classical Doppler Effect 17
1.4.2 Relativistic Doppler Effect 18
1.5 COSMOLOGICAL REDSHIFT AND THE EXPANDING UNIVERSE 20
1.6 DISTANCE AND AGE CALCULATIONS 23
QUESTIONS AND PROBLEMS 27
Chapter 2(cid:2) Propagation of Radiation 29
2.1 RADIATIVE TRANSFER 29
2.1.1 Absorption of Radiation 29
2.1.2 Emission of Radiation 32
2.1.3 General Radiative Transfer Equation 35
v
vi (cid:2) Contents
2.2 PROPAGATION IN AN IONIZED MEDIUM 37
2.2.1 Plasma Frequency 37
2.2.2 Dispersion Measure 39
2.2.3 Faraday Rotation 41
QUESTIONS AND PROBLEMS 45
Chapter 3(cid:2) Continuum Emission Processes 47
3.1 RADIATION FROM ACCELERATED CHARGES 47
3.2 THERMAL RADIATION 50
3.2.1 Blackbody Radiation 51
3.2.2 Rayleigh-Jeans Approximation 60
3.2.3 Brightness Temperature 62
3.2.4 Thermal Bremsstrahlung Radiation (or Free-Free Emission) 63
3.3 NON-THERMAL RADIATION 67
3.3.1 Cyclotron Radiation 67
3.3.2 Synchrotron Radiation by a Single Relativistic Electron 70
3.3.3 Radiation by an Ensemble of Relativistic Electrons 73
3.3.4 Polarization of Synchrotron Radiation 75
3.3.5 Optical Depth Effects: Synchrotron Self-Absorption 76
QUESTIONS AND PROBLEMS 79
Chapter 4(cid:2) Spectral Lines 83
4.1 EMISSION AND ABSORPTION LINES 85
4.1.1 Einstein Coefficients 85
4.1.1.1 Spontaneous Emission 86
4.1.1.2 Absorption 88
4.1.1.3 Stimulated Emission 89
4.1.1.4 Absorption Coefficient 90
4.1.1.5 Relations between the Einstein A and B Coefficients 91
4.1.2 Line Broadening 91
4.1.3 Spectral Line Radiative Transfer 93
4.1.4 Kirchhoff’s Rules for Spectroscopy 95
4.1.5 Collisional Transition Rates and Excitation Temperature 96
4.2 RADIO SPECTRAL LINES 101
4.2.1 21-cm Spectral Line of Atomic Hydrogen 101
4.2.2 Radio Recombination Spectral Lines 107
4.2.3 Molecular Rotational Spectral Lines 108
QUESTIONS AND PROBLEMS 118
Contents (cid:2) vii
Chapter 5(cid:2) The Cold Interstellar Medium of the Milky Way 121
5.1 21-CM SPECTRAL LINE OF ATOMIC HYDROGEN 124
5.1.1 Observations of the 21-cm Line 124
5.1.2 Rotation Curve of the Galaxy 129
5.1.3 Distribution of HI in the Milky Way 131
5.1.4 Absorption Lines - Warm and Cold Gas 133
5.1.5 Magnetic Field 137
5.2 OBSERVATIONS OF THE ROTATIONAL LINES OF MOLECULES 137
5.2.1 Molecular Clouds 138
5.2.2 Distribution of Molecular Clouds in the Galaxy 146
5.2.3 Molecular Cloud Cores 147
5.2.4 Astrochemistry 152
5.3 OBSERVATIONS OF THE THERMAL EMISSION FROM DUST 153
5.3.1 Dust Extinction 154
5.3.2 Dust Emission 155
5.3.3 Global Distribution of Dust 159
QUESTIONS AND PROBLEMS 160
Chapter 6(cid:2) HII Regions and Planetary Nebulae at Radio Wavelengths 163
6.1 HII REGIONS 163
6.1.1 Ionization Structure of HII Regions 164
6.1.2 The Temperature of HII Regions 169
6.1.3 Time Scales of HII Regions 171
6.2 RADIO EMISSION FROM HII REGIONS 172
6.2.1 Bremsstrahlung Emission from HII Regions 172
6.2.2 Radio Recombination Line Emission from HII Regions 176
6.2.3 Gas Density and Temperature from RRLs:
Non-Equilibrium Effects 182
6.3 THE CLASSIFICATION AND EVOLUTION OF HII REGIONS 184
6.3.1 Classification of HII Regions 184
6.3.2 Evolution of HII Regions 185
6.4 PLANETARY NEBULAE 188
QUESTIONS AND PROBLEMS 189
Chapter 7(cid:2) Radio Emission from Stellar Objects 191
7.1 SOLAR RADIO EMISSION 191
7.1.1 The Quiet Sun 191
7.1.2 Slowly Varying Component of the Sun 194
viii (cid:2) Contents
7.1.3 Radio Bursts 196
7.2 RADIO EMISSION FROM STARS 196
7.2.1 Thermal Radio Emission 196
7.2.1.1 Main Sequence Stars 197
7.2.1.2 Giant and Supergiant Stars 198
7.2.2 Winds from Asymptotic Giant Branch Stars 199
7.2.3 Flare Stars 200
7.3 YOUNG STARS 201
7.3.1 Proto-stellar Disks 201
7.3.2 Thermal Radio Jets 203
7.3.3 Molecular Outflows 204
7.4 RADIO PULSARS 206
7.4.1 Pulsar Mechanics 208
7.4.2 Pulsar Emission Mechanisms 213
7.4.3 Pulsar Searches 216
7.4.4 Binary Pulsars 218
7.4.5 Radio Pulsars as Probes of the Interstellar Medium 218
7.4.6 Supernova Remnants 220
QUESTIONS AND PROBLEMS 222
Chapter 8(cid:2) Galaxies at Radio Wavelengths 225
8.1 21-CM HI OBSERVATIONS 227
8.1.1 HI Mass of Galaxies 228
8.1.2 Imaging HI in Galaxies 232
8.2 MOLECULAR GAS IN GALAXIES 236
8.2.1 Molecular Gas Mass 237
8.2.2 Imaging CO in Galaxies 240
8.2.3 Other Molecules in Galaxies 241
8.3 RADIO CONTINUUM EMISSION FROM GALAXIES 243
8.3.1 Dust Emission 244
8.3.2 Long Wavelength Radio Continuum Emission 247
8.4 DISTANT GALAXIES 249
QUESTIONS AND PROBLEMS 254
Chapter 9(cid:2) Radio Galaxies and Quasars 257
9.1 BRIEF OVERVIEW OF ACTIVE GALACTIC NUCLEI 257
9.2 AGN MODEL 263
9.3 MORPHOLOGIES, SIZES, AND SPECTRA OF RADIO
GALAXIES AND QUASARS 268
Contents (cid:2) ix
9.3.1 Synchrotron Spectrum from an Inhomogeneous Source 272
9.3.2 Free-free Absorption of Synchrotron Radiation 274
9.3.3 Inverse Compton Scattering and the Compton Limit 276
9.4 INFERRING PHYSICAL CONDITIONS IN AGN 277
9.4.1 Spectral Index Maps 278
9.4.2 Kinematic Studies 280
9.4.3 Magnetic Field Estimates 286
9.4.4 Electron Cooling Timescales and the Nature of Hot Spots
in Jets 288
9.5 THE CENTER OF THE MILKY WAY 290
QUESTIONS AND PROBLEMS 291
Chapter 10(cid:2) Cosmic Microwave Background 295
10.1 COSMOLOGICAL MODELS 295
10.2 BLACKBODY NATURE OF THE CMB 297
10.3 ANISOTROPIES IN THE CMB 300
10.4 COSMOLOGICAL PARAMETERS 304
10.5 CMB POLARIZATION 306
QUESTIONS AND PROBLEMS 307
Appendix A(cid:2) Constants and Conversions 311
Appendix B(cid:2) Mathematica Code for Calculating Age of Universe
and Distances for Given Redshift 313
Appendix C(cid:2) Complex-Valued Wave Functions 315
Appendix D(cid:2) Derivations of the Effects of Propagation of Radiation
in Ionized Media 319
D.1 BASIC EQUATIONS OF ELECTROMAGNETIC WAVES 319
D.2 APPLICATIONS TO REAL MEDIA 321
D.2.1 Dissipative Media 322
D.2.2 The Plasma Frequency Equation 324
D.2.3 Derivation of the Wave Velocity as a Function of Frequency
and the Arrival Time of a Pulse 324
D.3 DERIVATION OF THE ROTATION ANGLE OF POLARIZATION
IN MAGNETIZED MEDIA 325
