Testing cosmological structure formation using redshift-space distortions

TL;DR

This paper introduces a new statistic based on redshift-space distortions in galaxy surveys that is bias-independent and matches the matter power spectrum, enabling better constraints on cosmological structure growth.

Contribution

Develops and tests a novel anisotropy-based statistic in galaxy power spectra that is bias-independent and effective on large scales for probing structure formation.

Findings

The new statistic matches the matter power spectrum shape on large scales.

It provides constraints on the derivative of the linear growth rate, f.sigma_8.

A Gaussian damping model effectively describes quasi-linear behavior.

Abstract

Observations of redshift-space distortions in spectroscopic galaxy surveys offer an attractive method for observing the build-up of cosmological structure. In this paper we develop and test a new statistic based on anisotropies in the measured galaxy power spectrum, which is independent of galaxy bias and matches the matter power spectrum shape on large scales. The amplitude provides a constraint on the derivative of the linear growth rate through f.sigma_8. This demonstrates that spectroscopic galaxy surveys offer many of the same advantages as weak lensing surveys, in that they both use galaxies as test particles to probe all matter in the Universe. They are complementary as redshift-space distortions probe non-relativistic velocities and therefore the temporal metric perturbations, while weak lensing tests the sum of the temporal and spatial metric perturbations. The degree to which our estimator can be pushed into the non-linear regime is considered and we show that a simple Gaussian damping model, similar to that previously used to model the behaviour of the power spectrum on very small scales, can also model the quasi-linear behaviour of our estimator. This enhances the information that can be extracted from surveys for LCDM models.