The WiggleZ Dark Energy Survey: measuring the cosmic growth rate with the two-point galaxy correlation function

TL;DR

This paper measures the cosmic growth rate up to redshift 0.9 using galaxy correlation functions from the WiggleZ survey, providing insights into dark energy and structure formation with results consistent with the standard cosmological model.

Contribution

It introduces a method to measure the growth rate of cosmic structure using the two-point galaxy correlation function across multiple redshift slices, validated against simulations and independent analyses.

Findings

Growth rate measurements are consistent with ΛCDM predictions.

The pairwise velocity dispersion increases with decreasing redshift.

Results are robust against model assumptions and systematic errors.

Abstract

The growth history of large-scale structure in the Universe is a powerful probe of the cosmological model, including the nature of dark energy. We study the growth rate of cosmic structure to redshift $z = 0.9$ using more than $162{,}000$ galaxy redshifts from the WiggleZ Dark Energy Survey. We divide the data into four redshift slices with effective redshifts $z = [0.2,0.4,0.6,0.76]$ and in each of the samples measure and model the 2-point galaxy correlation function in parallel and transverse directions to the line-of-sight. After simultaneously fitting for the galaxy bias factor we recover values for the cosmic growth rate which are consistent with our assumed $\Lambda$CDM input cosmological model, with an accuracy of around 20% in each redshift slice. We investigate the sensitivity of our results to the details of the assumed model and the range of physical scales fitted, making close comparison with a set of N-body simulations for calibration. Our measurements are consistent with an independent power-spectrum analysis of a similar dataset, demonstrating that the results are not driven by systematic errors. We determine the pairwise velocity dispersion of the sample in a non-parametric manner, showing that it systematically increases with decreasing redshift, and investigate the Alcock-Paczynski effects of changing the assumed fiducial model on the results. Our techniques should prove useful for current and future galaxy surveys mapping the growth rate of structure using the 2-dimensional correlation function.