New Approaches to Modeling Statistics of the Large-scale Structure in the Universe
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Date
2014-06-30
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Johns Hopkins University
Abstract
The spatial distribution of matter in the universe is a powerful probe of cosmology due in large part to the Baryon Acoustic Oscillation (BAO) feature in the 2-point correlation function, which provides a standard ruler that allows us to measure the properties of dark energy. Current and future galaxy surveys promise to deliver vast amounts of data and systematic errors will become dominant over statistical errors in determining cosmological parameters from galaxy surveys. Accurate theoretical models of systematics such as nonlinear gravitational evolution and redshift-space distortions are necessary to extract cosmological information from the statistics of large-scale structure.
First, we present a configuration-space approach to perturbation theory. We show how this can be used to calculate the nonlinear contribution to the 2-point correlation function, and verify the result both analytically and numerically. We then extend this approach to include the effects of redshift-space distortions. Our results indicate that a configuration-space approach to perturbation theory simplifies the mathematics of the nonlinear and redshift-space statistics of the matter distribution.
Next, we consider the effects of density transformations on the bias of the BAO peak in the 2-point correlation function. Using configuration-space perturbation theory, we model the nonlinear correlation functions of various transformed fields and find that a logarithmic transform, which results in a more Gaussian distribution, provides a less biased peak position at low redshift. Such a transform could improve constraints on dark energy parameters.
Because the nonlinear density field is non-Gaussian, information resides in higher-point statistics of the distribution. The 3-point statistics of the galaxy density field contain information about inflation, structure formation, and galaxy bias. Extracting this information requires accurate modeling of nonlinearity and redshift-space distortions. We discuss the challenges associated with theoretical and numerical modeling of the bispectrum on nonlinear scales, and test current models in various regimes. We then show how a configuration-space approach can be used to model the redshift-space 3-point correlation function in a simple way.
By modeling nonlinearity and redshift-space distortions in the statistics of the matter distribution we can better constrain cosmological parameters from galaxy surveys.
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Keywords
Cosmology, Large-scale structure of the Universe, Baryon Acoustic Oscillations