The WiggleZ Dark Energy Survey: Final data release and cosmological results

TL;DR

The paper reports the final WiggleZ data release and cosmological results from a comprehensive galaxy power-spectrum analysis across four redshift bins, incorporating seven modelling approaches for non-linearities, bias, and redshift-space distortions calibrated against the GiggleZ simulations. By combining WiggleZ P(k) with CMB, BAO, LSS, and SN-Ia data, the study finds results consistent with flat ΛCDM, yielding Ω_m ≈ 0.29 and σ_8 ≈ 0.825, while placing upper bounds on extensions such as the neutrino mass ∑ m_ν, the running of the spectral index n_run, and the tensor-to-scalar ratio r. Among modelling schemes, a simulation-calibrated approach without BAO damping (Model G) best recovers the fiducial cosmology in GiggleZ, and is used as the default in CosmoMC analyses. The work demonstrates the importance of accurately modelling non-linear growth, galaxy bias, and redshift-space distortions, and provides public data and a CosmoMC module to enable broader cosmological analyses with WiggleZ data. Overall, all results are consistent with ΛCDM, while the WiggleZ dataset significantly tightens constraints on several cosmological parameters and supports the robustness of standard cosmology for the observed large-scale structure up to z ≈ 1.

Abstract

This paper presents cosmological results from the final data release of the WiggleZ Dark Energy Survey. We perform full analyses of different cosmological models using the WiggleZ power spectra measured at z=0.22, 0.41, 0.60, and 0.78, combined with other cosmological datasets. The limiting factor in this analysis is the theoretical modelling of the galaxy power spectrum, including non-linearities, galaxy bias, and redshift-space distortions. In this paper we assess several different methods for modelling the theoretical power spectrum, testing them against the Gigaparsec WiggleZ simulations (GiggleZ). We fit for a base set of 6 cosmological parameters, {Omega_b h^2, Omega_CDM h^2, H_0, tau, A_s, n_s}, and 5 supplementary parameters {n_run, r, w, Omega_k, sum m_nu}. In combination with the Cosmic Microwave Background (CMB), our results are consistent with the LambdaCDM concordance cosmology, with a measurement of the matter density of Omega_m =0.29 +/- 0.016 and amplitude of fluctuations sigma_8 = 0.825 +/- 0.017. Using WiggleZ data with CMB and other distance and matter power spectra data, we find no evidence for any of the extension parameters being inconsistent with their LambdaCDM model values. The power spectra data and theoretical modelling tools are available for use as a module for CosmoMC, which we here make publicly available at http://smp.uq.edu.au/wigglez-data . We also release the data and random catalogues used to construct the baryon acoustic oscillation correlation function.

Figures (19)

• Figure 1: (color online). The WiggleZ power spectrum in the four redshift bins, weighted averaged over the seven regions. We artificially offset the redshift bins in the vertical direction to distinguish them (with the lowest redshift bin at the bottom moving up to highest at the top). At each redshift the line gives the best fit flat-$\Lambda$CDM cosmology prediction, convolved with the window function for each region and then averaged over the regions. The shaded region gives the range in wavenumber of data we used for the analysis.
• Figure 2: (color online). The WiggleZ covariance matrix in the four redshift bins, as a weighted average over the seven regions.
• Figure 3: (color online). ( top): A weighted average of the WiggleZ power spectra in the survey regions and redshifts, and the seven models described in section \ref{['sec:Approaches']} for the best fit cosmology of the best model (G). ( bottom): The same models, but now the power spectrum has been rated to the linear prediction. In both plots the shaded region from $k=0.02\,h\,\textrm{Mpc}^{-1}$ to $k=0.3\,h\,\textrm{Mpc}^{-1}$ is the range of data we are using in our analysis. This shows the divergence of models at large $k$ and the reason why careful modelling is necessary.
• Figure 4: (color online). 1 and $2\sigma$ contours for in the {$\Omega_m$, $f_b$} plane for fits to the GiggleZ power spectra using model A-G. All other cosmological parameters are held fixed at the GiggleZ fiducial cosmology (WMAP 5-year best fit values). The GiggleZ parameter values are marked by a cross. The red ellipses (model E) lie directly on top of the green ones (model B), and so are not visible. This shows that the choice of model has a significant effect on the cosmological constraints from the power spectrum. Our preferred model is the Model G, which successfully reproduces the input parameters of the GiggleZ simulation.
• Figure 5: ( Top) Reduced $\chi^2$ of models fitted to the $N$-body simulation halo catalogue for the GiggleZ fiducial cosmology values. In absence of systematic errors the models should recover the input cosmology with $\chi^2/\mathrm{dof} \simeq1$. ( Bottom) Difference in reduced $\chi^2$ values when using the GiggleZ fiducial cosmological parameters and the best fit values.