Published in Physics Reports, Volume 530, Issue 2, p. 87-255, 2013.
http://arxiv.org/abs/1201.2434

For a PDF version of the article, click here.

OBSERVATIONAL PROBES OF COSMIC ACCELERATION

1,2 David H. Weinberg 2 Michael J. Mortonson 3,4 Daniel J. Eisenstein 5 Christopher Hirata 6 Adam G. Riess 7 Eduardo Rozo


1 Department of Astronomy, Ohio State University, Columbus, OH
2 Center for Cosmology and Astro-Particle Physics, Ohio State University, Columbus, OH
3 Steward Observatory, University of Arizona, Tucson, AZ
4 Harvard College Observatory, Cambridge, MA
5 California Institute of Technology, Pasadena, CA
6 Department of Physics and Astronomy, Johns Hopkins University, Baltimore, MD
7 Kavli Institute for Cosmological Physics, University of Chicago, Chicago, IL


Abstract: The accelerating expansion of the universe is the most surprising cosmological discovery in many decades, implying that the universe is dominated by some form of "dark energy" with exotic physical properties, or that Einstein's theory of gravity breaks down on cosmological scales. The profound implications of cosmic acceleration have inspired ambitious efforts to understand its origin, with experiments that aim to measure the history of expansion and growth of structure with percent-level precision or higher. We review in detail the four most well established methods for making such measurements: Type Ia supernovae, baryon acoustic oscillations (BAO), weak gravitational lensing, and the abundance of galaxy clusters. We pay particular attention to the systematic uncertainties in these techniques and to strategies for controlling them at the level needed to exploit "Stage IV" dark energy facilities such as BigBOSS, LSST, Euclid, and WFIRST. We briefly review a number of other approaches including redshift-space distortions, the Alcock-Paczynski effect, and direct measurements of the Hubble constant H0. We present extensive forecasts for constraints on the dark energy equation of state and parameterized deviations from General Relativity, achievable with Stage III and Stage IV experimental programs that incorporate supernovae, BAO, weak lensing, and cosmic microwave background data. We also show the level of precision required for clusters or other methods to provide constraints competitive with those of these fiducial programs. We emphasize the value of a balanced program that employs several of the most powerful methods in combination, both to cross-check systematic uncertainties and to take advantage of complementary information. Surveys to probe cosmic acceleration produce data sets that support a wide range of scientific investigations, and they continue the longstanding astronomical tradition of mapping the universe in ever greater detail over ever larger scales.


Table of Contents

INTRODUCTION
History
Theories of Cosmic Acceleration
Looking Forward

OBSERVABLES, PARAMETERIZATIONS, AND METHODS
Basic Equations
Model Parameterizations
CMB Anisotropies and Large Scale Structure
Parameter Dependences and CMB Constraints
Overview of Methods

TYPE Ia SUPERNOVAE
General Principles
The Current State of Play
Observational Considerations
Systematic Uncertainties and Strategies for Amelioration
Space vs. Ground
Prospects

BARYON ACOUSTIC OSCILLATIONS
General Principles
The Current State of Play
Theory of BAO
Linear Theory
Non-linear Evolution and Galaxy Clustering Bias
Reconstruction
Fitting to Data
Observational Considerations
Statistical Errors
From BAO to Dark Energy
Sampling Density
Spectroscopic vs. Photometric Redshifts
Tracers of Structure
Systematic Uncertainties and Strategies for Amelioration
Measurement Systematics
Astrophysical Systematics
Cosmological Systematics
Space vs. Ground
Prospects

WEAK LENSING
General principles: Overview
Weak lensing principles: Mathematical discussion
Deflection of light in cosmology
Cosmic shear, magnification, and flexion
Power spectra and correlation functions*
Method I: Cosmic Shear Power Spectrum*
Method II: Power Spectrum Tomography*
Method III: Galaxy-galaxy Lensing*
Method IV: Cosmography*
Method V: Non-Gaussian Statistics*
The Current State of Play
Cosmic shear
Galaxy-galaxy lensing as a cosmological probe
Lensing outside the optical bands
Observational Considerations and Survey Design
Statistical Errors
The Galaxy Population for Optical Surveys
Photometric Redshifts and their Calibration
Lensing in the Radio
Lensing of the CMB
Measuring Shears
The Idealized Problem
Shape Measurement Algorithms*
Shape Measurement Errors*
Noise Rectification and Selection Biases*
Determining the PSF and Instrument Properties
Astrophysical systematics
Intrinsic Alignments*
Theoretical uncertainties in the matter power spectrum*
Systematic Errors and their Amelioration: Summary
Advantages of a Space Mission
Prospects

CLUSTERS OF GALAXIES
General Principles
The Current State of Play
Observational Considerations
Expected Numbers and Cosmological Sensitivity
Cluster Finding
Calibrating the Observable-Mass Relation
Systematic Uncertainties and Strategies for Amelioration
Redshift Uncertainties
Contamination and Incompleteness: The Tails of P(X|M,z)
Calibrating the Core of P(X|M,z)
Theoretical Systematics
Space vs. Ground
Prospects

ALTERNATIVE METHODS
Measurement of the Hubble Constant at z ≈ 0
Redshift-Space Distortions
The Alcock-Paczynski Test
Alternative Distance Indicators
Standard Sirens
The Lyα Forest as a Probe of Structure Growth
Other Tests of Modified Gravity
The Integrated Sachs-Wolfe Effect
Cross-Correlation of Weak Lensing and Spectroscopic Surveys
Strong Gravitational Lenses
Galaxy Ages
Redshift Drift
Alternative Methods: Summary

A BALANCED PROGRAM ON COSMIC ACCELERATION
A Fiducial Program
Forecasting Constraints
Results: Forecasts for the Fiducial Program and Variations
Constraints in simple w(z) models
Constraints on structure growth parameters
Dependence on w(z) model and binning of data
Constraints on w(z) in the general model
Forecasts for Clusters
Forecasts for Alternative Methods
The Hubble constant
The Alcock-Paczynski Test
Redshift-space Distortions
Distances
Observables and Aggregate Precision
Prospects with Many Probes

CONCLUSIONS

APPENDIX A. GLOSSARY OF ACRONYMS AND FACILITIES

REFERENCES

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