The Galactic Center in Motion
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The Galactic Center In Motion Philipp M. Plewa München 2018 The Galactic Center In Motion Philipp M. Plewa Dissertation an der Fakultät für Physik der Ludwig–Maximilians–Universität München vorgelegt von Philipp M. Plewa aus Warendorf München, den 27.4.2018 Erstgutachter: Professor Reinhard Genzel Zweitgutachter: Professor Andreas Burkert Tag der mündlichen Prüfung: 2.7.2018 Contents Summary xiii 1 Introduction: The inner nuclear star cluster and its black hole 1 2 A Sgr A* rest frame for high-precision Galactic Center astrometry 9 2.1 Introduction . 9 2.2 Image processing . 11 2.2.1 Observations . 11 2.2.2 Image reduction . 12 2.2.3 Star lists . 12 2.3 A distortion correction for NACO . 14 2.3.1 Star matching . 14 2.3.2 The distortion model . 14 2.4 The Sgr A* rest frame . 18 2.4.1 Image registration . 18 2.4.2 Testing the distortion correction . 20 2.4.3 The astrometric reference stars . 20 2.4.4 The location of Sgr A* . 24 2.5 Discussion & Conclusions . 26 2.A A distortion correction for NACO (II) . 28 2.A.1 A distortion correction for the S13 camera . 28 2.A.2 Mapping the image distortion . 28 2.A.3 The distortion model . 30 2.B Pixel scale and rotation angle . 31 2.C Supplementary figures . 32 3 The post-pericenter evolution of the Galactic Center source G2 33 3.1 Introduction . 34 3.2 Observations & Methods . 35 3.2.1 SINFONI data reduction . 35 3.2.2 NACO image processing . 36 3.2.3 Orbit fitting . 37 3.3 Results . 39 vi Table of Contents 3.3.1 The gas emission . 39 3.3.2 The dust emission . 43 3.4 Discussion . 44 3.4.1 G2 as a probe of the accretion zone . 44 3.4.2 The relationship between G2 and G1 . 47 3.4.3 The relationship between G2 and the tail . 47 3.5 Summary . 50 3.A Supplementary figures . 52 4 The properties and effects of unrecognized astrometric confusion 55 4.1 Introduction . 55 4.2 Methods . 56 4.2.1 Astrometric confusion . 56 4.2.2 The stellar background . 58 4.2.3 Noise modeling & Orbit fitting . 61 4.3 Results . 65 4.3.1 The flares of Sgr A* . 65 4.3.2 The orbits of the S-Stars . 68 4.3.3 Application to observations . 75 4.4 Conclusions . 77 5 A machine-learning approach to photometric stellar classification 79 5.1 Introduction . 79 5.2 Observations & Data reduction . 80 5.3 Methods . 81 5.3.1 Photometry . 83 5.3.2 Classification . 84 5.4 Results . 87 5.4.1 Classification performance . 87 5.4.2 The stellar population . 89 5.5 Conclusions . 91 6 Conclusion & Outlook 93 Bibliography 99 Acknowledgements 113 List of Figures 1.1 The Galactic Center environment (multi-band image) . 2 1.2 The Galactic Center environment (schematic diagram) . 3 1.3 The Keplerian orbit of the star S2 . 6 2.1 Example PSF grid . 13 2.2 S27 camera distortions . 15 2.3 Timeline of NACO observations . 16 2.4 Astrometric error models . 19 2.5 Image registration residuals . 19 2.6 Motions of the SiO maser stars . 21 2.7 Drift of the astrometric coordinate system . 22 2.8 Precision and stability of the Sgr A* rest frame . 26 2.9 S13 camera distortions . 29 2.10 Pixel scale and rotation angle . 30 2.11 Positions of the astrometric reference stars . 32 3.1 Position-velocity diagrams . 39 3.2 Line maps . 40 3.3 Radial velocity distributions . 41 3.4 Radial velocity maps . 42 3.5 Luminosity evolution . 42 3.6 Orbit orientation . 43 3.7 L-band images . 44 3.8 Drag force limits . 45 3.9 Extended (tail) pv-diagram . 48 3.10 Extended (tail) image . 49 3.11 Posterior distribution of model parameters . 52 3.12 Comparison of Ks- and L’-band images . 53 3.13 Motion of G2 in L’-band images . 53 3.14 Line maps (tail) . 54 4.1 Example confusion event (I) . 57 4.2 Example confusion event (II) . 57 viii List of Figures 4.3 Example S-Star trajectories . 61 4.4 Test case for astrometric confusion (I) . 66 4.5 Test case for astrometric confusion (II) . 67 4.6 Test case for astrometric confusion (III) . 67 4.7 Test case for astrometric confusion (IV) . 68 4.8 Predicted perturbations to measurements . 69 4.9 Example GP model fit . 70 4.10 Posterior distribution of hyper-parameters . 71 4.11 Bias of the black hole mass and distance . 72 4.12 Bias of the orbital parameters . 74 4.13 Best-fit parameters . 75 5.1 Filter transmission curves . 82 5.2 Example spectra (I) . 82 5.3 Example spectra (II) . 83 5.4 Calibration maps . 85 5.5 Classification results . 86 5.6 Classification performance . 88 5.7 Surface density profile and luminosity function . 90 5.8 Learning curve . 91 List of Tables 2.1 Summary of globular cluster observations . 11 2.2 Summary of Galactic Center observations . 12 2.3 Basis vector fields . 17 2.4 Motions of the SiO maser stars . 23 2.5 Alignment of the SiO maser stars . 25 3.1 Summary of model parameters . 45 4.1 Summary of main simulation parameters. ..