The Black Hole At The Galactic Center (2005)(en)(284s)

Eckart A.1-86094-5674

Reviewing the fundamental instrumental techniques and current observational results, this book unveils the mysteries of the physical processes in the central parsec of our Milky Way: the super-massive black hole embedded in a central stellar cluster as well as the gas and dust in the circumnuclear region.The observations described cover the entire electromagnetic spectrum from decimeter radio-waves to high energy X-ray and Y-rays, and a comprehensive summary of up-to-date astrophysical interpretations is given.The emphasis is put on observational techniques, image processing aspects, and a detailed presentation of the most cutting-edge work carried out in the near-infrared wavelength regime. These recent results include both the first orbits of stars around the central black hole and the multiwavelength variability of the central source.

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Table of contents :
Contents……Page 20
Preface……Page 6
1.1 The GC Across the Electromagnetic Spectrum……Page 24
1.1.1 Radio Wavelengths……Page 25
1.1.2 Far-Infrared Wavelengths……Page 30
1.1.3 Near- and Mid-Infrared Wavelengths……Page 35
1.1.4 Optical Wavelengths……Page 39
1.1.5 X-Ray Energies……Page 40
1.1.6 y-Ray Energies……Page 43
1.2 NIR Imaging Through the Atmosphere……Page 45
1.3 Speckle Imaging……Page 49
1.3.1 The Knox-Thompson Method……Page 53
1.3.2 The Bispectrum Analysis……Page 54
1.3.3 Seeing Calibration of Fourier Data……Page 55
1.3.4 The Shift-and-Add Algorithm……Page 56
1.3.5 Speckle Spectroscopy……Page 60
1.3.6 Speckle Instrumentation……Page 62
1.3.6.1 SHARP……Page 63
1.3.6.2 NIRC……Page 64
1.4.1 Adaptive Optics Imaging……Page 65
1.4.2 Adaptive Optics Spectroscopy……Page 72
1.4.3.1 NAOS/CONICA……Page 74
1.4.3.3 PUEO……Page 77
1.4.3.5 HOKUPA’A……Page 78
1.4.3.6 FASTTRAC……Page 79
1.5 Cleaning and Deconvolution……Page 80
1.5.1 Linear Deconvolution……Page 81
1.5.2 Lucy-Richardson Deconvolution……Page 83
1.5.3 Estimating the PSF……Page 84
1.5.4 Iterative Blind Deconvolution……Page 85
1.5.5 Comparison of Deconvolution Algorithms……Page 86
1.6 Future IR Interferometry……Page 89
1.6.1 VLTI……Page 90
1.6.2 Keck Interferometer……Page 92
1.6.3 LBT LINC/NIRVANA……Page 93
2.1 The Discovery of Sagittarius A……Page 94
2.2 Large-Scale Structures at the Galactic Center……Page 96
2.3 The Circum Nuclear Disk……Page 99
2.4 The Mini-Spiral……Page 100
2.5 Radio Filaments……Page 102
2.6.1 A Brief History of NIR Imaging……Page 103
2.6.2 Diffraction Limited Images……Page 106
2.7 The Radio and lnfrared Positional Reference Frames……Page 109
2.8 Number Density Counts……Page 111
2.8.1 Evidence for a Central Stellar Cusp……Page 115
2.8.2 K-band Luminosity Function……Page 118
2.9.1 Extended Filaments in the Sgr A Complex……Page 123
2.9.2 Polarized Emission from Stars……Page 126
2.10 Stellar Velocities and Orbital Accelerations……Page 128
2.10.1 Measuring Stellar Proper Motions……Page 129
2.10.3 Motions in the Inner Cluster……Page 131
2.10.4 Accelerations of Stars Near Sgr A……Page 135
2.10.5 Stellar Orbits……Page 136
2.11 Spectroscopy……Page 140
2.11.1 Stellar Populations……Page 141
2.11.2 The Upper Mass Cut-Off……Page 143
2.11.3 The Central Arcsecond……Page 145
2.11.4.1 Extraction and Calibration of Spectra……Page 146
2.11.4.2 Spectra in the Central Sgr A* Cluster……Page 147
2.11.5 Adaptive Optics Spectroscopy of the Central Cusp……Page 148
2.12 Star Formation at the Galactic Center?……Page 151
2.12.1 Embedded Objects……Page 153
2.12.2 IR-Excess Objects……Page 154
2.13.1 Size and Spectrum of Sgr A* at Radio Wavelengths……Page 159
2.13.2 Polarization of Sgr A* at Radio Wavelengths……Page 164
2.13.3 Sgr A* as a Variable X-Ray Source……Page 166
2.13.4 Sgr A* as a Variable NIR Source……Page 168
2.13.5 How Likely are Strong NIR Flares?……Page 173
2.13.6 First Simultaneous X-Ray/NIR Detection of Sgr A*……Page 175
3. Astrophysical Results……Page 178
3.1 The Stellar Velocity Field……Page 179
3.2 Scenarios for Star Formation at the Galactic Center……Page 183
3.2.1 Infall of Stellar Clusters……Page 184
3.2.2 In Situ Formation from Dense Gas……Page 187
3.2.3 Formation of Stars in the Mini-Spiral……Page 188
3.3.1 First Order Estimates……Page 190
3.3.2 Mass Estimators……Page 191
3.3.3 The Jeans Method……Page 192
3.3.4 The Orbit of the Star S2……Page 196
3.3.6 A Lower Limit to the Mass……Page 197
3.4 Stability of the Enclosed Dark Mass……Page 198
3.5 Agglomerations of Exotic Particles?……Page 201
3.6.1 Spatial Distribution of the Stars……Page 204
3.6.2 Velocity Distribution of the Stars……Page 206
3.6.4 Young, Massive Stars in the Cusp……Page 208
3.6.5 Dynamics of the Cusp and Presence of Young Stars……Page 209
3.7 Analysis of Stellar Orbits Near the Central Black Hole……Page 212
3.7.1 Relativistic Periastron Shift……Page 213
3.7.2 Lense-Thirring Precession……Page 214
3.7.4 Orbits in a Uniform Density Sphere……Page 216
3.7.5 Stellar Deflections……Page 217
3.7.6 Constraints from non-Keplerian Orbits……Page 219
3.8 The Central Black Hole……Page 222
3.8.1 Standard Accretion Theory……Page 223
3.8.2 The Low Luminosity of Sgr A*……Page 224
3.8.3 Radiatively Inefficient Accretion Flow Models……Page 225
3.8.4 Sgr A* Flare Models……Page 230
3.8.5 A Spin Measurement of the Black Hole?……Page 233
3.8.6 Gravitational Disk Modes……Page 235
3.9 Comparison to Nuclei of Other Galaxies……Page 238
3.10 Massive Black Holes at High Redshifts……Page 241
Appendix A Color Versions of Selected Figures……Page 246
Appendix B Table of Individual Sources……Page 260
Appendix C Useful Quantities……Page 264
Appendix D Table of Abbreviations……Page 266
Bibliogruphy……Page 272
Index……Page 296