Astronomy at High Angular Resolution: A Compendium of Techniques in the Visible and Near-Infrared (Astrophysics and Space Science Library Book 439)

This Book Offers An Essential Compendium Of Astronomical High-resolution Techniques. Recent Years Have Seen Considerable Developments In Such Techniques, Which Are Critical To Advances In Many Areas Of Astronomy. As Reflected In The Book, These Techniques Can Be Divided Into Direct Methods, Interferometry, And Reconstruction Methods, And Can Be Applied To A Huge Variety Of Astrophysical Systems, Ranging From Planets, Single Stars And Binaries To Active Galactic Nuclei, Providing Angular Resolution In The Micro- To Tens Of Milliarcsecond Scales. Written By Experts In Their Fields, The Chapters Cover Adaptive Optics, Aperture Masking Imaging, Spectra Disentangling, Interferometry, Lucky Imaging, Roche Tomography, Imaging With Interferometry, Interferometry Of Agn, Agn Reverberation Mapping, Doppler- And Magnetic Imaging Of Stellar Surfaces, Doppler Tomography, Eclipse Mapping, Stokes Imaging, And Stellar Tomography. This Book Is Intended To Enable A Next Generation Of Astronomers To Apply High-resolution Techniques. It Informs Readers On How To Achieve The Best Angular Resolution In The Visible And Near-infrared Regimes From Diffraction-limited To Micro-arcsecond Scales. Introduction By The Editors -- Adaptive Optics -- Aperture Masking Imaging -- Disentangling Of Stellar Spectra -- Interferometry -- Lucky Imaging -- Roche Tomography -- Spectro-astrometry -- Astrotomography Of Planets -- Adaptive Optics Of Planets & Disks -- Stellar Surfaces With Interferometry -- The Galactic Centre At High-angular Resolution -- Agn Interferometry -- Agn Reverberation Mapping -- Doppler And Magnetic Imaging Of Stellar Surfaces -- Doppler Tomography -- Doppler Tomography Of Polars -- Doppler Imaging Of Cool Stars And Brown Dwarfs -- Eclipse Mapping -- Stokes Imaging. Edited By Henri M. J. Boffin, Gaitee Hussain, Jean-philippe Berger, Linda Schmidtobreick. Preface 8 Contents 10 List of Contributors 16 1 Lucky Imaging in Astronomy 18 1.1 Motivations for Employing Lucky Imaging Techniques 18 1.2 Atmospheric Seeing ``101'' and Lucky Imaging 19 1.2.1 Angular Resolution and the Fried Parameter r0 20 1.2.2 Strehl Ratio 20 1.2.3 Coherence Time τ0 20 1.2.4 Probability of Lucky Imaging 21 1.3 Lucky Imaging Precursors 23 1.4 Technical Implementation 24 1.5 Observing and Data Reduction Strategy 27 1.6 Lucky Imaging Compared to Other High-Angular Resolution Techniques 28 1.6.1 Passive Techniques 29 1.6.2 Active Techniques 29 1.6.3 Combining Passive and Active Techniques 29 1.6.4 Additional Advantages and Limitations of Lucky Imaging 30 1.7 Examples for Instrumentation and Science 30 1.8 Summary and Outlook 31 References 32 2 Adaptive Optics in High-Contrast Imaging 34 2.1 Introduction 34 2.1.1 Science Case 34 2.1.2 Requirements 35 2.1.3 From Pioneering Adaptive Optics Experiments to Extreme Adaptive Optics System 38 2.2 Fundamentals of High-Contrast Adaptive Optics Systems 39 2.2.1 Characteristics of Images Distorted by the Atmospheric Turbulence 39 2.2.1.1 Architecture of an AO System 40 2.2.2 Wavefront Sensing 40 2.2.3 Deformable Mirror Technologies 42 2.3 The Transition to Extreme AO Systems 42 2.3.1 Wavefront Error Requirement for High Contrast 43 2.3.2 Coronagraphy and Diffraction Control 45 2.3.3 Low-Order Wavefront Sensing and Non-common Path Aberrations 47 2.3.4 Observation Strategies for Improved Stability and Speckle Removal 47 2.3.4.1 Stability Considerations 47 2.3.4.2 Observing Strategies 48 2.4 Science Highlights and New Challenges 51 2.4.1 Discs at Very Short Separations 51 2.4.2 Planets in the Visible 52 2.4.3 Spectra of Exoplanets and Brown Dwarfs 53 2.5 Conclusions and Future Challenges 54 References 54 3 Aperture Masking Imaging 59 3.1 Introduction 59 3.2 Narrow Field Imaging 60 3.3 Non-redundant Aperture Masking 63 3.4 Kernel and Bispectral Phase 67 3.5 Applications of Aperture-Masking Imaging 70 3.5.1 Precision Binary Astrometry 71 3.5.2 Faint, Low-Strehl Imaging 71 3.5.3 High-Contrast Imaging (e.g. LkCa 15) 71 3.6 Conclusions 72 References 73 4 Optical Long Baseline Interferometry 74 4.1 Linking the Object to the Interference Fringes 74 4.1.1 Interference of a Single Emitter 74 4.1.2 Linearity Between the Emitter and the Fringes Displacements 76 4.1.3 Integration Over Many Emitters 76 4.2 Interpreting Interferometric Observations 77 4.2.1 Partially Resolved: Diameter Measurements 77 4.2.2 Parametric Analysis 80 4.2.3 Aperture Synthesis Imaging 82 4.3 Instrumentation Suite 84 4.3.1 Observing Facilities 84 4.3.2 Support and Observing Tools 86 4.4 Conclusions 87 References 87 5 Image Reconstruction in Optical Interferometry: An Up-to-Date Overview 89 5.1 Introduction 89 5.2 Principles of Optical Interferometry 90 5.3 Bayesian Framework of Image Reconstruction 91 5.3.1 Bayes Equation for Image Reconstruction 91 5.4 Likelihood 92 5.4.1 Non-convexity and Multi-modality of the Likelihood 92 5.5 Regularisation 93 5.5.1 Separable Regularisation Functions 94 5.5.2 Example of Regulariser: Prior Images 94 5.5.3 Example of Regulariser: Multiscale Approaches and Compressed Sensing 96 5.5.3.1 Compressed Sensing 96 5.5.3.2 Applying Compressed Sensing to Optical Interferometry 97 5.5.3.3 Dictionaries for Optical Interferometry 97 5.5.4 Regularisation Weight 98 5.6 Optimisation Engines: The Software Landscape 100 5.6.1 Stochastic vs Deterministic Approaches 100 5.6.1.1 Classic Deterministic Algorithms 100 5.6.1.2 Stochastic Algorithms 101 5.6.1.3 Explicit vs Implicit Approach and Self-Calibration 102 5.6.1.4 Multiwavelength: Proximal Methods 102 5.6.2 Fidelity of Current Reconstructions 103 5.7 Conclusion 104 References 104 6 Tori, Discs, and Winds: The First Ten Yearsof AGN Interferometry 108 6.1 Active Galactic Nuclei 101 108 6.2 The Dusty Environment 109 6.3 Infrared Long-Baseline Interferometry of AGN: Pushing the Limits 110 6.4 Science Results 111 6.4.1 Sizes and What They Mean 111 6.4.2 The Dust Is Clumpy, Indeed! 114 6.4.3 The Inner Radius Scales with Luminosity, But What Kind of Dust Are We Seeing? 114 6.4.4 Constraints on the Volume Filling Factor 116 6.4.5 The Distribution of the Dust Revealed, But It Is Not Clear What It Means 118 6.4.6 Where Is the Torus After All? 120 6.5 Conclusions and Outlook 121 References 123 7 Disentangling of Stellar Spectra 126 7.1 Introduction 126 7.2 Disentangling of Spectra of Multiple Stars 127 7.2.1 Fourier Disentangling 129 7.2.2 Generalised Disentangling 131 7.2.3 Constrained Disentangling 133 7.2.4 Numerical Representation 135 7.3 Disentangling of Spectra of Interacting Binaries 136 Appendix: Bayesian Estimation of Parameters Errors 138 Errors of Line Strengths and Radial Velocities 139 Errors in Multidimensional Space of Parameters 142 References 147 8 Velocity Fields in Stellar Atmospheres Probed by Tomography 149 8.1 Introduction 149 8.2 Method 151 8.3 Results 154 8.3.1 Application to the Mira Variables RT Cyg and RY Cep 155 8.3.2 Other Pulsating Variables 156 8.3.3 Supergiants 159 8.4 Future Prospects: Transforming Optical Depths to Geometrical Depths to Access the Shock Velocity 163 References 163 9 Eclipse Mapping: Astrotomography of Accretion Discs 166 9.1 Context and Motivations 166 9.2 Principles and Inner Workings 167 9.3 Performance and Limitations 173 9.4 Error Propagation Procedures 177 9.5 Applications 177 9.5.1 Spectral Mapping: Spatially-Resolved Disc Spectra 177 9.5.2 Time-Lapse Mapping: Dwarf Nova Outbursts 179 9.5.3 Flickering Mapping: Revealing the Disc Viscosity 181 9.5.4 3D Eclipse Mapping: Disc Opening Angle and Superhumps 183 9.6 Summary 184 References 185 10 Stokes Imaging: Mapping the Accretion Region(s) in Magnetic Cataclysmic Variables 189 10.1 Introduction 189 10.2 Polarisation Modelling 190 10.3 Stokes Imaging 193 10.4 Photo-polarimetric Observations of the Eclipsing Polar CTCV J1928-5001 194 10.5 Future Work: Stratified Accretion Shocks 195 10.6 Future Work: Multi-tomography 199 References 202 11 Doppler Tomography 205 11.1 Introduction 205 11.2 Principles of Doppler Tomography 206 11.2.1 Coordinates 206 11.2.2 3D Profile Formation 209 11.2.3 2D Profile Formation 210 11.2.4 Inversion 211 11.2.4.1 Filtered Back-projection 212 11.2.4.2 Regularised Fitting 212 11.2.5 Doppler Tomography Extras 214 11.2.5.1 Systemic Velocity 215 11.2.5.2 Orbital Phase Uncertainty 215 11.2.5.3 Finite Exposures 215 11.2.5.4 Blended Lines 216 11.2.5.5 Modulation Mapping 216 11.2.6 Codes for Doppler Tomography 216 11.3 Doppler Tomography in Practice 217 11.3.1 Spiral Shocks 217 11.3.2 Donor Star Emission 218 11.3.3 AM CVn Stars 218 11.4 Doppler Tomography of Polars: Accretion Streams, Accretion Curtains and Half Stars 220 11.4.1 Accretion Streams and Curtains 221 11.4.2 Accretion Curtains in Asynchronous Polars 226 11.4.3 The Donor Stars 227 11.4.4 Summary on Polars 229 References 229 12 Tomographic Imaging of Stellar Surfaces and Interacting Binary Systems 233 12.1 Doppler and Zeeman-Doppler Imaging of Stellar Surfaces 233 12.1.1 Doppler Imaging as a Tool to Study StellarMagnetism 233 12.1.2 Principles of Doppler Imaging (DI) 235 12.1.3 Measurements of Stellar Magnetic Fields and Zeeman-Doppler Imaging 237 12.1.4 Zeeman-Doppler Imaging Science Highlights 242 12.1.4.1 Chemically Peculiar Stars 243 12.1.4.2 Cool Main Sequence Stars 243 12.1.4.3 Classical T Tauri Stars 244 12.1.4.4 Ongoing and Future Developments 244 12.2 Roche Tomography 247 12.2.1 The Motivation for Roche Tomography 247 12.2.2 The Principles of Roche Tomography 248 12.2.3 Roche Tomography: Early Maps 249 12.2.4 Probing Stellar Activity 251 12.2.5 Differential Rotation 252 12.2.6 Future Prospects 253 12.2.6.1 Problems to be Solved 253 12.2.6.2 Future Directions and Opportunities 253 References 254 13 AGN Reverberation Mapping 259 13.1 Introduction and Motivation 259 13.2 Reverberation Mapping Primer 260 13.3 Reverberation Mapping Products 264 13.3.1 Black Hole Masses 264 13.3.2 Black Hole Scaling Relationships 267 13.3.3 BLR Geometry and Kinematics 269 13.4 Looking Ahead 272 References 273 Index 277 Front Matter....Pages i-xvi Lucky Imaging in Astronomy....Pages 1-16 Adaptive Optics in High-Contrast Imaging....Pages 17-41 Aperture Masking Imaging....Pages 43-57 Optical Long Baseline Interferometry....Pages 59-73 Image Reconstruction in Optical Interferometry: An Up-to-Date Overview....Pages 75-93 Tori, Discs, and Winds: The First Ten Years of AGN Interferometry....Pages 95-112 Disentangling of Stellar Spectra....Pages 113-135 Velocity Fields in Stellar Atmospheres Probed by Tomography....Pages 137-153 Eclipse Mapping: Astrotomography of Accretion Discs....Pages 155-177 Stokes Imaging: Mapping the Accretion Region(s) in Magnetic Cataclysmic Variables....Pages 179-194 Doppler Tomography....Pages 195-222 Tomographic Imaging of Stellar Surfaces and Interacting Binary Systems....Pages 223-248 AGN Reverberation Mapping....Pages 249-266 Back Matter....Pages 267-274