The WiggleZ Dark Energy Survey: the growth rate of cosmic structure since redshift z=0.9

TL;DR

This paper measures the growth rate of cosmic structure across redshifts 0.1 to 0.9 using WiggleZ survey data, supporting the flat LCDM model and providing new insights into velocity divergence and galaxy bias.

Contribution

It provides the first measurements of the velocity divergence power spectrum and tests galaxy bias models, enhancing understanding of structure growth and dark energy.

Findings

Growth rate measurements are consistent with flat LCDM model.

First measurement of the velocity divergence power spectrum P_vv(k).

WiggleZ galaxy bias is scale-independent for k < 0.3 h/Mpc.

Abstract

We present precise measurements of the growth rate of cosmic structure for the redshift range 0.1 < z < 0.9, using redshift-space distortions in the galaxy power spectrum of the WiggleZ Dark Energy Survey. Our results, which have a precision of around 10% in four independent redshift bins, are well-fit by a flat LCDM cosmological model with matter density parameter Omega_m = 0.27. Our analysis hence indicates that this model provides a self-consistent description of the growth of cosmic structure through large-scale perturbations and the homogeneous cosmic expansion mapped by supernovae and baryon acoustic oscillations. We achieve robust results by systematically comparing our data with several different models of the quasi-linear growth of structure including empirical models, fitting formulae calibrated to N-body simulations, and perturbation theory techniques. We extract the first measurements of the power spectrum of the velocity divergence field, P_vv(k), as a function of redshift (under the assumption that P_gv(k) = -sqrt[P_gg(k) P_vv(k)] where g is the galaxy overdensity field), and demonstrate that the WiggleZ galaxy-mass cross-correlation is consistent with a deterministic (rather than stochastic) scale-independent bias model for WiggleZ galaxies for scales k < 0.3 h/Mpc. Measurements of the cosmic growth rate from the WiggleZ Survey and other current and future observations offer a powerful test of the physical nature of dark energy that is complementary to distance-redshift measures such as supernovae and baryon acoustic oscillations.