Cosmic 21-cm Revolution: Charting the First Billion Years of our Universe

Description

The redshifted 21-cm signal is set to transform astrophysical cosmology, bringing a historically data-starved field into the era of Big Data. Corresponding to the spin-flip transition of neutral hydrogen, the 21-cm line is sensitive to the temperature and ionization state of the cosmic gas, as well as to cosmological parameters. Crucially, with the development of new interferometers it will allow us to map out the first billion years of our Universe, enabling us to learn about the properties of the unseen first generations of galaxies. Rapid progress is being made on both the observational and theoretical fronts, and important decisions on techniques and future direction are being made. The Cosmic 21-cm Revolution gathers contributions from current leaders in this fast-moving field, providing both an overview for graduate students and a reference point for current researchers. PRELIMS.pdf Preface Editor biography Andrei Mesinger Contributors CH001.pdf Chapter 1 Theoretical Framework: The Fundamentals of the 21 cm Line 1.1 Radiative Transfer of the 21 cm Line 1.2 The Spin Temperature 1.2.1 Collisional Coupling 1.2.2 The Wouthuysen–Field Effect 1.3 Heating of the Intergalactic Medium 1.3.1 The Lyα Background 1.3.2 The Cosmic Microwave Background 1.3.3 The X-Ray Background 1.3.4 Other Potential Heating Mechanisms References CH002.pdf Chapter 2 Astrophysics from the 21 cm Background 2.1 Properties of the High-z Intergalactic Medium 2.1.1 The Brightness Temperature 2.1.2 Basics of Nonequilibrium Ionization Chemistry 2.1.3 Ionization and Heating around Point Sources 2.1.4 Ionization and Heating on Large Scales 2.1.5 Lyα Coupling 2.2 Sources of the UV and X-Ray Background 2.2.1 Star Formation 2.2.2 UV Emission from Stars 2.2.3 Attenuation of Stellar UV Emission by Dust 2.2.4 Escape of UV Photons from Galaxies 2.2.5 X-Rays from Stellar-mass Black Holes 2.2.6 X-Rays from Shocks and Hot Gas 2.2.7 Escape of X-Rays from Galaxies 2.2.8 Cosmic Rays from Supernovae 2.3 Predictions for the 21 cm Background 2.3.1 Dependence on the Ionizing Efficiency 2.3.2 Dependence on the X-Ray Efficiency and Spectrum 2.3.3 Dependence on the Lyα Efficiency 2.3.4 Dependence on Stellar Metallicity 2.3.5 Dependence on the Minimum Mass 2.4 Summary References CH003.pdf Chapter 3 Physical Cosmology from the 21 cm Line 3.1 Introduction 3.2 Cosmology in the Dark Ages 3.2.1 Setting the Stage: The Standard Cosmological Paradigm 3.2.2 The Global 21 cm Signal during the Dark Ages 3.2.3 The Power Spectrum during the Dark Ages 3.3 Cosmology during the Era of Astrophysics 3.3.1 Isolating the Matter Power Spectrum 3.3.2 Redshift Space Distortions 3.3.3 Indirect Effects of Cosmology on the 21 cm Background 3.4 21 cm Cosmology in a Larger Context References CH004.pdf Chapter 4 Inference from the 21 cm Signal 4.1 What Do We Actually Measure? 4.2 Optimal Methods for Characterizing the 21 cm Signal 4.2.1 Global Signal 4.2.2 Power Spectrum 4.2.3 Bispectrum 4.2.4 Trispectrum 4.2.5 One-point Statistics 4.2.6 Wavelets 4.2.7 Topological Measurements of the 21 cm Signal 4.2.8 Bubble-size Distributions 4.2.9 Individual Images 4.2.10 Stacked Images 4.2.11 Multifield Approaches 4.3 Modeling the 21 cm Signal 4.3.1 Numerical Simulations 4.3.2 Seminumerical and Analytic Models of the 21 cm Signal 4.3.3 Intelligent Sampling of the Parameter Space 4.3.4 Emulators 4.3.5 Characterizing Our Ignorance 4.4 Inference Methods for the 21 cm Signal 4.4.1 Fisher Matrices 4.4.2 Fixed Grid Sampling 4.4.3 Bayesian MCMC 4.4.4 Model Selection and Nested Sampling 4.4.5 Neural Networks References CH005.pdf Chapter 5 21 cm Observations: Calibration, Strategies, Observables 5.1 Interferometry Overview 5.2 21 cm Observables: Power Spectra and Images 5.3 Interferometric Calibration and 21 cm Observations 5.3.1 Redundant Calibration 5.4 Array Design and Observing Strategies 5.5 Conclusions 5.6 Acknowledgments References CH006.pdf Chapter 6 Foregrounds and Their Mitigation 6.1 What Are the Foregrounds? 6.1.1 Galactic Foregrounds in Total Intensity 6.1.2 Extragalactic Foregrounds in Total Intensity 6.1.3 Polarized Foregrounds 6.1.4 Radio Frequency Interference 6.2 Foreground Mitigation 6.2.1 Foreground Mitigation in the Data Analysis Pipeline 6.2.2 Foreground Avoidance and Suppression 6.2.3 Foreground Subtraction 6.2.4 Residual Error Subtraction 6.2.5 Polarization Leakage 6.3 Conclusions References http://adsabs.harvard.edu/abs/1982A&AS...47....1H%3C/ext-link%3E%3C/element-citation%3E%3C/ref%3E%3Cref id= http://adsabs.harvard.edu/abs/1982A&AS...47....1H%3C/ext-link%3E%3C/element-citation%3E%3C/ref%3E%3Cref id= CH007.pdf Chapter 7 Global Signal Instrumentation 7.1 Introduction 7.2 Radiometer Basics 7.2.1 Antenna 7.2.2 Receiver 7.2.3 Digitzer 7.3 Challenges Facing Experiments 7.3.1 Antenna Radiation Efficiency 7.3.2 Antenna Transfer Efficiency 7.3.3 Gain Pattern 7.3.4 Cosmic Foregrounds 7.3.5 Ionosphere 7.3.6 Polarization 7.3.7 Interference 7.4 Précis of Design Requirements 7.5 Outside the Box Architectures 7.5.1 Single-element Sensor Radiometer 7.5.2 Outriggers to Fourier Synthesis Telescopes 7.5.3 Interferometric Methods 7.5.4 Zero-spacing Interferometer 7.5.5 Lunar Occultation References CH008.pdf Chapter 8 Status of 21 cm Interferometric Experiments 8.1 Introduction 8.2 Early Work 8.3 Experimental Methodologies and Current Experiments 8.3.1 Giant Metrewave Radio Telescope—GMRT 8.3.2 Murchison Widefield Array—MWA 8.3.3 Low Frequency Array—LOFAR 8.3.4 Precision Array for Probing the Epoch of Reionization—PAPER 8.4 Published Results 8.5 Current Challenges 8.6 Prospects for the Future 8.6.1 Current Instruments 8.6.2 Future Instruments 8.6.3 Future Analyses References CH009.pdf Chapter 9 Future Prospects 9.1 What Drives Future 21 cm Signal Experiment? 9.1.1 Limits of Current 21 cm Signal Observations 9.1.2 What Will Drive Future 21 cm Experiments? 9.2 Ground-based Interferometers 9.2.1 The Square Kilometre Array—SKA1&2 9.2.2 The Hydrogen Epoch of Reionization Array—HERA 9.2.3 The Large Aperture Experiment to Detect the Dark Ages—LEDA 9.2.4 The Low Frequency Array 2.0—LOFAR2.0 9.2.5 The Murchison Widefield Array Phase II 9.2.6 New Extension in Nançay Upgrading LOFAR—NenuFAR 9.3 Global Signal Experiments 9.3.1 The Experiment to Detect the Global EoR Signature—EDGES 9.3.2 The Large Aperture Experiment to Detect the Dark Ages—LEDA (Global Signal) 9.3.3 Shaped Antennas to Measure the Background Radio Spectrum—SARAS 9.4 Space-based Instruments 9.4.1 The Dark Ages Polarimetry Pathfinder—DAPPER 9.4.2 Discovering the Sky at the Longest Wavelengths—DSL 9.4.3 Farside Array for Radio Science Investigations of the Dark Ages and Exoplanets—FARSIDE 9.4.4 Netherlands–China Low Frequency Explorer—NCLE 9.5 The Far Future of 21 cm Cosmology References