The WiggleZ Dark Energy Survey: the selection function and z=0.6 galaxy power spectrum

TL;DR

This study presents a robust determination of the three-dimensional galaxy power spectrum $P(k)$ at effective redshift $z\approx 0.6$ from 56{,}159 WiggleZ redshifts, using a carefully constructed survey selection function that accounts for angular and radial completeness and redshift blunders. The authors implement an optimized FKP estimator, model redshift-space distortions, and perform extensive Monte Carlo forward modeling to correct for systematic effects, achieving about 5% accuracy in $P(k)$ up to $k\approx 0.4\,h\,\mathrm{Mpc}^{-1}$. They extract growth-rate measurements $f(z)$ in the range $0.4<z<0.8$, finding results consistent with $\Lambda$CDM predictions, and perform preliminary fits to matter and baryon densities that align with CMB constraints. The work demonstrates the viability of high-redshift spectroscopic surveys for precision cosmology, enabling BAO studies, growth-history constraints, and tests of Gaussian initial conditions in upcoming WiggleZ data releases.

Abstract

We report one of the most accurate measurements of the three-dimensional large-scale galaxy power spectrum achieved to date, using 56,159 redshifts of bright emission-line galaxies at effective redshift z=0.6 from the WiggleZ Dark Energy Survey at the Anglo-Australian Telescope. We describe in detail how we construct the survey selection function allowing for the varying target completeness and redshift completeness. We measure the total power with an accuracy of approximately 5% in wavenumber bands of dk=0.01 h/Mpc. A model power spectrum including non-linear corrections, combined with a linear galaxy bias factor and a simple model for redshift-space distortions, provides a good fit to our data for scales k < 0.4 h/Mpc. The large-scale shape of the power spectrum is consistent with the best-fitting matter and baryon densities determined by observations of the Cosmic Microwave Background radiation. By splitting the power spectrum measurement as a function of tangential and radial wavenumbers we delineate the characteristic imprint of peculiar velocities. We use these to determine the growth rate of structure as a function of redshift in the range 0.4 < z < 0.8, including a data point at z=0.78 with an accuracy of 20%. Our growth rate measurements are a close match to the self-consistent prediction of the LCDM model. The WiggleZ Survey data will allow a wide range of investigations into the cosmological model, cosmic expansion and growth history, topology of cosmic structure, and Gaussianity of the initial conditions. Our calculation of the survey selection function will be released at a future date via our website wigglez.swin.edu.au.

Figures (22)

• Figure 1: Histograms of the values of GALEX exposure time and Galactic dust extinction across the WiggleZ survey regions analyzed in this paper.
• Figure 2: Differential source counts of GALEX-SDSS galaxy matches in bins of GALEX exposure time. We restrict the analysis to regions of the survey with low dust extinction $E_{B-V} < 0.04$. We note that the uppermost curve with the caption "$6000 < {\rm exp} < 99999$" corresponds to the "fiducial" source count in the limit of low dust extinction and high GALEX exposure time, as discussed in the text.
• Figure 3: Differential source counts of GALEX-SDSS galaxy matches in bins of dust extinction. We restrict the analysis to regions of the survey with GALEX exposure times $1400 < t_{\rm exp} < 1800$ sec.
• Figure 4: Dependence of the completeness parameter $\mu$ on dust extinction, in bins of exposure time. The measurements of $\mu$ are of highest quality for the dominant exposure time range $1400 < t_{\rm exp} < 1800$ sec. The error range in $\mu$ is asymmetric about the best-fitting value because the model becomes increasingly insensitive to $\mu$ as the value of $\mu$ increases. The measurement for each dust bin is plotted at the median value of $E_{B-V}$ for that bin.
• Figure 5: Fraction of GALEX-SDSS matches that are selected as WiggleZ targets as a function of GALEX $NUV$ magnitude.