Analysis of Structure on Galactic and Extragalactic Scales
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ANALYSIS OF STRUCTURE ON GALACTIC AND EXTRAGALACTIC SCALES By Qingqing Mao Dissertation Submitted to the Faculty of the Graduate School of Vanderbilt University in partial fulfillment of the requirements for the degree of DOCTOR OF PHILOSOPHY in PHYSICS August, 2015 Nashville, Tennessee Approved: Dr. Andreas A. Berlind Dr. Robert J. Scherrer Dr. Kelly Holley-Bockelmann Dr. Thomas J. Weiler Dr. M. Shane Hutson ACKNOWLEDGMENTS I am most thankful for the supervision of my advisor Dr. Andreas Berlind. This dissertation would not be possible without his mentorship and guidance. I am grateful to the members of my committee for taking time from their busy schedules to help me along this journey. They have all played critical roles in my development as a scientist. I am extremely grateful to my collaborators for all of their helpful suggestions, vibrant discussions and insightful advice on my research projects. I am also grateful to the SDSS collaboration for providing a fertile environment to conduct my research. I would like to thank my fellow graduate students and friends, especially the crew on the 9th floor. Without their support and friendship, my Ph.D. life would not have been so enjoyable, and I would have never made it this far. Finally, I would like to thank my mother Ziqiang Xu and father Lei Mao. They have always been a constant source of support and love throughout all of my pursuits in life. Thanks to Luxi Wang, whose patience, encouragement, and companionship has kept me going. ii TABLE OF CONTENTS Page ACKNOWLEDGMENTS .............................. ii LIST OF TABLES .................................. v LIST OF FIGURES.................................. vi I Introduction ................................... 1 I.1 The Expanding Universe and LCDM Model ................ 2 I.2 The Very Early Universe and Inflation.................... 3 I.3 Large-Scale Structure of the Universe.................... 5 I.4 Milky Way Structure............................. 7 I.5 Sloan Digital Sky Survey .......................... 8 I.5.1 BOSS ................................ 9 I.5.2 SEGUE ............................... 11 I.6 N-body Simulations and Mock Catalogs .................. 12 I.6.1 N-body Simulations in General................... 12 I.6.2 Redshift Space Distortions ..................... 13 I.6.3 LasDamas Simulations ....................... 15 I.6.4 Quick Particle-Mesh Simulations and Mocks............ 16 I.7 Summary................................... 17 II Constraining Primordial Non-Gaussianity with Moments of the Large Scale Density Field ................................... 18 II.1 Introduction ................................. 19 II.2 Background Theory ............................. 22 II.2.1 Skewness and Kurtosis ....................... 22 II.2.2 Non-Gaussian Initial Distribution.................. 23 II.2.3 Galaxy Bias ............................. 25 II.2.4 Discrete Distribution......................... 27 II.3 Simulated Data................................ 28 II.3.1 LasDamas Simulations ....................... 28 II.3.2 Mock Galaxy Catalogs ....................... 29 II.3.3 Survey Equivalent Volumes..................... 30 II.4 Results.................................... 31 II.4.1 Dark Matter ............................. 31 II.4.2 Mock Galaxy Catalogs ....................... 34 iii II.4.3 SDSS-II and BOSS Equivalent Volumes .............. 39 II.4.4 Scaling Down to Realistic fNL Values................ 46 II.4.5 Comparison With Existing Measurements ............. 48 II.5 Summary and Discussion .......................... 49 III A Cosmic Void Catalog of SDSS DR12 BOSS Galaxies............ 52 III.1 Introduction ................................. 52 III.2 LSS catalog and QPM mocks........................ 54 III.3 Void finding algorithm............................ 56 III.4 Void catalogs................................. 58 III.5 Void statistics and properties......................... 61 III.5.1 Size and redshift distributions.................... 61 III.5.2 Density profiles ........................... 64 III.5.3 Stellar mass distributions ...................... 68 III.6 Conclusions ................................. 70 IV Alcock-Paczynski´ Test Using Cosmic Voids in BOSS DR12 ......... 71 IV.1 Introduction ................................. 71 IV.2 Alcock-Paczynski´ Test............................ 73 IV.3 Data and mocks ............................... 74 IV.4 Finding voids................................. 75 IV.5 Stacking voids................................ 77 IV.6 Shape measurements............................. 79 IV.7 Cosmological constraints .......................... 83 IV.8 Discussion and conclusion.......................... 87 V Probing Galactic Structure with the Spatial Correlation Function of SEGUE G-dwarf Stars .................................. 95 V.1 Introduction ................................. 95 V.2 SEGUE G-dwarf Sample .......................... 97 V.3 Two-point Correlation Function Measurements . 101 V.4 Fitting A Smooth Galactic Model......................107 V.5 Evidence of Substructure?..........................113 V.6 Summary and Discussion ..........................115 VI CONCLUSIONS.................................117 A List of Cosmic Voids ...............................119 REFERENCES ....................................161 iv LIST OF TABLES Table Page II.1 The estimated survey volumes needed to have a 50% likelihood of de- tecting each non-Gaussian model by measuring the variance or the skew- ness..................................... 48 III.1 Part of the void catalog from the BOSS CMASS North sample. 59 A.1 List of voids in the BOSS CMASS North sample . 120 A.2 List of voids in the BOSS CMASS South sample . 139 A.3 List of voids in the BOSS LOWZ North sample . 145 A.4 List of voids in the BOSS LOWZ South sample . 156 v LIST OF FIGURES Figure Page I.1 History of the Universe .......................... 3 I.2 An illustration of large-scale structure................... 6 I.3 BOSS DR12 sky coverage......................... 10 I.4 An example of N-body simulations..................... 12 I.5 An illustration presenting how peculiar velocities lead to the redshift distortions (Hamilton 1997)......................... 14 I.6 Smoothed distribution of halos of a 40 h−1Mpc thick slice of the four LasDamas simulation boxes........................ 15 II.1 Variance, skewness, and kurtosis measurements for the dark matter dis- tribution in the Gaussian and non-Gaussian simulations ......... 32 II.2 Variance, skewness, and kurtosis measurements for dark matter particles and mock galaxy catalogs ......................... 35 II.3 The effect of galaxy bias on the variance and skewness residuals of non- Gaussian models with respect to the Gaussian model........... 36 II.4 The effect of redshift distortions on the variance and skewness residuals of non-Gaussian models with respect to the Gaussian model . 37 II.5 Variance and skewness measurements on SDSS-II (left panels) and BOSS (right panels) equivalent volumes ..................... 40 II.6 The probability that a measurement of variance, skewness, or kurtosis in the BOSS galaxy survey can be used to detect a deviation from the Gaussian model .............................. 42 II.7 The probability that a measurement of higher order moments in the BOSS galaxy survey can be used to detect a deviation from the Gaussian model.................................... 44 vi II.8 A comparison of the existing measurements of variance, skewness and kurtosis from SDSS-II data with the measurements from our Gaussian simulations................................. 49 III.1 A thin slice of CMASS galaxies...................... 57 III.2 Distribution of void sizes.......................... 62 III.3 Distribution of void redshift........................ 63 III.4 Distance from void center to the nearest survey boundary compared to void effective radius............................ 65 III.5 A slice through the stacked void...................... 66 III.6 1-Dimensional stacked density profile of voids.............. 67 III.7 The stellar mass distribution of all galaxies and void galaxies . 69 IV.1 A slice of the stacked void......................... 78 IV.2 An analytical test of our method of shape measurement ......... 80 IV.3 Ratio between the measured axis ratio and the assumed axis ratio versus the assumption............................... 81 IV.4 The distribution of the shape of the stacked voids measured from QPM mock catalogs ............................... 82 IV.5 Shape measurements of the stacked voids assuming different Wm . 85 IV.6 The probability distribution of Wm ..................... 86 IV.7 Shape measurements using different size of spheroids .......... 88 IV.8 Testing the effect of squashing in redshift space by smoothing the veloc- ity field................................... 90 IV.9 The effect of the tracer density on the shape of the stacked voids . 91 IV.10 Predictions of how the uncertainty in Wm scales with the survey volume . 93 vii V.1 Sky map of the SEGUE fields used in this study, shown in a Mollweide projection in Galactic coordinates..................... 97 V.2 A selection of SEGUE pencil beam fields in a slice that is perpendicular to the Galactic plane and includes the Galactic center........... 98 V.3 Distribution of G-dwarf stars with distance, along a selection of nine SEGUE lines-of-sight ...........................100 V.4 Dependence of the correlation function on the underlying density gradient103 V.5 Dependence of the correlation function on survey geometry . 105 V.6 The two-point correlation