Astrophysics

Preface to the 1^st edition xiii

Preface to the 2^nd edition xv

Acknowledgments - 1st Edition xvii

Acknowledgments - 2nd Edition xix

List of Symbols xxi

About the Companion

Website xxiii

Introduction xxv

I.1 Dimensions, Units and Equations xxix

Problems xxxiv

Just for Fun xxxiv

Part I: The Nonelectromagnetic Signal 1

Chapter 1: The Particles: Macroscopic to Subatomic 3

1.1 Meteoritics 4

1.1.1 Dating Meteorites 7

1.1.2 Infrasound 9

1.1.3 Gathering Dust 15

1.2 Cosmic Rays 17

1.2.1 Cosmic Ray Composition 18

1.2.2 The Cosmic Ray Energy Spectrum 19

1.2.3 The Origin of Primary Cosmic Rays 23

1.3 Neutrinos 25

1.3.1 The Neutrino Spectrum 27

1.3.2 Astrophysics with Neutrinos 30

Problems 32

Just for Fun 35

Chapter 2: Gravitational Radiation: A New Window 37

2.1 Concepts of Relativity 37

2.2 The Fabric of Space-Time 38

2.3 Curved Space-Time near a Mass 40

2.4 Gravitational Waves 43

2.5 GWs from Binary Orbits 45

2.6 Evolution of a Binary Orbit 48

2.6.1 The Inspiral 48

2.6.2 The 'Death-Spiral' 51

2.7 Indirect Proof of the Existence of Gravitational Waves 53

2.8 Direct Proof of the Existence of Gravitational Waves 55

2.9 Even Newer Windows 58

Problems 59

Just for Fun 60

Part II: The EM Signal Observed 63

Chapter 3: Defining the Signal 65

3.1 The Power of Light - Luminosity and Spectral Power 65

3.2 Light Through a Surface - Flux and Flux Density 69

3.3 The Brightness of Light - Intensity and Specific Intensity 72

3.4 Light from All Angles - Energy Density and Mean Intensity 78

3.5 How Light Pushes - Radiation Pressure 80

3.6 The Human Perception of Light - Magnitudes 83

3.6.1 Apparent Magnitude 83

3.6.2 Absolute Magnitude 86

3.6.3 The Colour Index and Bolometric Correction 86

3.6.4 Gaia and the HR Diagram 87

3.6.5 Magnitudes Beyond Stars 90

3.7 Light Aligned - Polarization 90

Problems 91

Just for Fun 95

Chapter 4: Measuring the Signal 97

4.1 Spectral Filters and the Panchromatic Universe 97

4.2 Catching the Signal - The Telescope 100

4.2.1 Collecting and Focussing the Signal 103

4.2.2 Detecting the Signal 105

4.2.3 Field of View and Pixel Resolution 107

4.2.4 Diffraction and Diffraction-limited Resolution 107

4.2.5 Weighting the Aperture - Interferometry 109

4.3 The Corrupted Signal - The Atmosphere 113

4.3.1 Atmospheric Refraction 113

4.3.2 Seeing 114

4.3.3 Adaptive Optics 118

4.3.4 Scintillation 121

4.3.5 Atmospheric Reddening 121

4.4 Processing the Signal 122

4.4.1 Correcting the Signal 122

4.4.2 Calibrating the Signal 123

4.5 Analysing the Signal 123

4.6 Visualizing the Signal 125

4.7 Comparing Signals in Disparate Wavebands 129

Problems 130

Just for Fun 132

Part III: Matter and Radiation Essentials 133

Chapter 5: Matter Essentials 135

5.1 The Big Bang 135

5.2 Dark and Light Matter 136

5.3 Abundances of the Elements 141

5.3.1 Primordial Abundance 141

5.3.2 Stellar Evolution and ISM Enrichment 141

5.3.3 Supernovae and Explosive Nucleosynthesis 146

5.3.4 Abundances in the Milky Way, Its Star Formation History and the IMF 149

5.4 The Gaseous Universe 154

5.4.1 Kinetic Temperature and the Maxwell- Boltzmann Velocity Distribution 157

5.4.2 The Ideal Gas 159

5.4.3 The Mean Free Path and Collision Rate 162

5.4.4 Statistical Equilibrium, Thermodynamic Equilibrium, and Local Thermodynamic Equilibrium 165

5.4.5 Excitation and the Boltzmann Equation 169

5.4.6 Ionization and the Saha Equation 173

5.4.7 Probing the Gas 174

5.5 The Dusty Universe 176

5.5.1 Observational Effects of Dust 177

5.5.2 Structure and Composition of Dust 182

5.5.3 The Origin of Dust 184

Problems 185

Just for Fun 187

Chapter 6: Radiation Essentials 189

6.1 Black Body Radiation 189

6.1.1 The Brightness Temperature 193

6.1.2 The Rayleigh-Jeans law and Wien's law 195

6.1.3 Wien's Displacement law and Stellar Colours 197

6.1.4 The Stefan-Boltzmann law, Stellar Luminosity and the HR Diagram 199

6.1.5 Energy Density and Pressure in Stars 200

6.2 Grey Bodies and Planetary Temperatures 201

6.2.1 The Equilibrium Temperature of a Grey Body 204

6.2.2 Exoplanets and Their Detection 209

Problems 213

Just for Fun 217

Part IV: The EM Signal Perturbed 219

Chapter 7: The Interaction of Light with Matter 221

7.1 The Photon Redirected - Scattering 222

7.1.1 Elastic Scattering 226

7.1.2 Inelastic Scattering 234

7.2 The Photon Lost - Absorption 238

7.2.1 Particle Kinetic Energy - Heating 238

7.2.2 Change of State - Ionization and the Strömgren Sphere 239

7.3 The Wavefront Redirected - Refraction 242

7.4 Quantifying Opacity and Transparency 245

7.4.1 Total Opacity and the Optical Depth 245

7.4.2 Dynamics of Opacity - Pulsation and Stellar Winds 249

7.5 The Opacity of Dust - Extinction 253

Problems 255

Just for Fun 259

Chapter 8: The Signal Transferred 261

8.1 Types of Energy Transfer 261

8.2 The Equation of Transfer 263

8.3 Solutions to the Equation of Transfer 265

8.3.1 Case A: No Cloud 265

8.3.2 Case B: Absorbing, but Not Emitting Cloud 266

8.3.3 Case C: Emitting, but Not Absorbing Cloud 266

8.3.4 Case D: Cloud in Thermodynamic Equilibrium (TE) 267

8.3.5 Case E: Emitting and Absorbing Cloud 267

8.3.6 Case F: Emitting and Absorbing Cloud in LTE 268

8.4 Implications of the LTE Solution 268

8.4.1 Implications for Temperature 268

8.4.2 Observability of Emission and Absorption Lines 269

8.4.3 Determining Temperature and Optical Depth of HI Clouds 276

Problems 279

Just for Fun 280

Chapter 9: The Interaction of Light with Space 281

9.1 Redshifts and Blueshifts 282

9.1.1 The Doppler Shift - Deciphering Dynamics 282

9.1.2 The Expansion Redshift 291

9.1.3 The Gravitational Redshift 294

9.2 Gravitational Refraction 295

9.2.1 Geometry and Mass of a Gravitational Lens 296

9.2.2 Microlensing - MACHOs and Planets 301

9.2.3 Cosmological Distances with Gravitational Lenses - Time Delays and H0 303

9.3 Time Variability and Source Size 305

9.4 A Brief Coda 305

Problems 306

Just for Fun 310

Part V: The EM Signal Emitted 311

Chapter 10: Continuum Emission 313

10.1 Characteristics of Continuum Emission - Thermal and Nonthermal 314

10.2 Bremsstrahlung (Free-Free) Emission 315

10.2.1 The Thermal Bremsstrahlung Spectrum 316

10.2.2 Radio Emission from HII and Other Ionized Regions 321

10.2.3 X-ray Emission from Hot Diffuse Gas 325

10.3 Free-Bound (Recombination) Emission 332

10.4 Two-Photon Emission 335

10.5 Synchrotron (and Cyclotron) Radiation 336

10.5.1 Cyclotron Radiation - Planets to Pulsars 339

10.5.2 The Synchrotron Spectrum 345

10.5.3 Determining Synchrotron Source Properties 349

10.5.4 Synchrotron Sources - Spurs, Bubbles, Jets, Lobes, and Relics 353

10.6 Inverse Compton Radiation 356

Problems 360

Just for Fun 363

Chapter 11: Line Emission 365

11.1 The Richness of the Spectrum - Radio Waves to Gamma Rays 366

11.1.1 Electronic Transitions - Optical and UV Lines 366

11.1.2 Rotational and Vibrational Transitions - Molecules, IR and mm-Wave Spectra 367

11.1.3 Nuclear Transitions - ¿¿¿¿-Rays and High Energy Events 371

11.2 The Line Strengths, Thermalization, and the Critical Gas Density 376

11.3 Line Broadening 378

11.3.1 Doppler Broadening and Temperature Diagnostics 378

11.3.2 Pressure Broadening 382

11.4 Probing Physical Conditions Via Electronic Transitions 384

11.4.1 Radio Recombination Lines 384

11.4.2 Optical Recombination Lines 390

11.4.3 The 21 Cm Line of Hydrogen 394

11.5 Probing Physical Conditions Via Molecular Transitions 398

11.5.1 The Carbon Monoxide (CO) Molecule 399

Problems 401

Just for Fun 403

Part VI: The Signal Decoded 405

Chapter 12: Forensic Astronomy 407

12.1 Complex Spectra 408

12.1.1 Isolating the Signal 408

12.1.2 Modelling the Signal 410

12.2 Case Studies - The Active, the Young, and the Old 415

12.2.1 Case Study 1: The Galactic Centre (the Active) 415

12.2.2 Case Study 2. The Cygnus Star-Forming Complex (the Young) 419

12.2.3 Case Study 3: The Globular Cluster, NGC 6397 (the Old) 422

12.3 The Messenger and the Message 426

Problems 427

Just for Fun 429

Appendix T 431

Acronym Key to

Bibliography 441

References and In-Depth

Reading 442

Index 467