The WiggleZ Dark Energy Survey: Improved Distance Measurements to z = 1 with Reconstruction of the Baryonic Acoustic Feature (1401.0358v2)

Abstract: We present significant improvements in cosmic distance measurements from the WiggleZ Dark Energy Survey, achieved by applying the reconstruction of the baryonic acoustic feature technique. We show using both data and simulations that the reconstruction technique can often be effective despite patchiness of the survey, significant edge effects and shot-noise. We investigate three redshift bins in the redshift range 0.2<$z$<1, and in all three find improvement after reconstruction in the detection of the baryonic acoustic feature and its usage as a standard ruler. We measure model independent distance measures $D_{\mathrm V}(r_{\mathrm s}^\mathrm{fid}/r_{\mathrm s})$ of 1716 $\pm$ 83 Mpc, 2221 $\pm$ 101 Mpc, 2516 $\pm$ 86 Mpc (68% CL) at effective redshifts z = 0.44, 0.6, 0.73, respectively, where $D_{\mathrm V}$ is the volume-average-distance, and $r_{\mathrm s}$ is the sound horizon at the end of the baryon drag epoch. These significantly improved 4.8, 4.5 and 3.4 percent accuracy measurements are equivalent to those expected from surveys with up to 2.5 times the volume of WiggleZ. These measurements are fully consistent with cosmologies allowed by the analyses of the Planck Collaboration and the Sloan Digital Sky Survey.We provide the $D_{\mathrm V}(r_{\mathrm s}^\mathrm{fid}/r_{\mathrm s})$ posterior probability distributions and their covariances. When combining these measurements with temperature fluctuations measurements of Planck, the polarization of WMAP9, and the 6dF Galaxy Survey baryonic acoustic feature, we do not detect deviations from a flat LCDM model. Assuming this model we constrain the current expansion rate to $H_0$ = 67.15 $\pm$ 0.98 kms$^{-1}$Mpc$^{-1}$. Allowing the equation of state of dark energy to vary we obtain $w_\mathrm{DE}$ = -1.080 $\pm$ 0.135. When assuming a curved LCDM model we obtain a curvature value of $\Omega_{\mathrm K}$ = -0.0043 $\pm$ 0.0047.

• The paper demonstrates that BAO reconstruction reduces cosmic distance measurement errors in the WiggleZ survey, with improvements from 7.9% to as low as 3.4%.
• The methodology dissects data into three redshift bins and employs mock catalogs to restore the BAO signature despite challenges like survey patchiness and shot noise.
• The refined measurements strengthen cosmological constraints by accurately determining parameters such as H0, ΩK, and the dark energy equation-of-state within a flat ΛCDM framework.

Analyzing Improved Cosmic Distance Measurements in the WiggleZ Dark Energy Survey Using Baryon Acoustic Oscillation Reconstruction

The paper "The WiggleZ Dark Energy Survey: Improved Distance Measurements to $z=1$ with Reconstruction of the Baryonic Acoustic Feature" presents a meticulous assessment of cosmic distances using the WiggleZ survey data, aiming to enhance these measurements by applying a reconstruction technique on the baryonic acoustic oscillation (BAO) feature. This endeavor, driven by the collaborative efforts of Kazin et al., addresses the challenges of survey patchiness, edge effects, and shot noise, establishing a more precise distance scale crucial for cosmological investigations.

Key Approaches and Results

The authors dissect the data into three redshift bins within the range $0.2 < z < 1.0$, conducting a comparative analysis pre- and post-reconstruction. Leveraging both actual data and simulated mock catalogs, they strive to restore the BAO signature, often blurred due to cosmic expansion and galaxy movements.

The results predominantly focus on the derived distance measurements denoted as $D_{\rm V}/r_{\rm s}$, with pre-reconstruction errors significantly refined post-reconstruction:

• At effective redshifts $z=0.44$, $z=0.6$, and $z=0.73$, the reconstruction enhances the precision from 7.9%, 6.0%, and 7.2% down to 4.8%, 4.5%, and 3.4%, respectively.
• Such improvements translate into measurements comparable to those expected from surveys two to three times larger than WiggleZ without applying reconstruction.

Implications for Cosmological Models

The precision imparted by reconstruction techniques elevates the utility of BAO as a standard ruler, instrumental in examining the parameters underlying cosmic acceleration models, notably the flat $\Lambda$CDM paradigm. Incorporating these refined measurements with Planck CMB temperature data and 6dFGS further reinforces the constraining power on cosmological parameters.

Among the notable cosmological parameter derivations, alongside assumptions of flatness and a constant dark energy equation of state ($w$),

• The current cosmic expansion rate $H_0$ is constrained to $67.15 \pm 0.98 \text{ km s}^{-1}\text{ Mpc}^{-1}$.
• Consideration of curvature yields $\Omega_K = -0.0043 \pm 0.0047$, suggesting a preference for a flat universe.
• A variable equation of state results in $w = -1.080 \pm 0.135$, aligning well with the cosmological constant model with $w = -1$.

Theoretical and Practical Contributions

This rigorous analysis delineates the application of reconstruction techniques in yielding improved, unbiased distance measurements from BAO features, especially important given WiggleZ's limited survey volume and sampling challenges. Such enhancements bear significant implications for the dark energy parameter space, promoting robustness in small-to-intermediate scale cosmic surveys.

Future Directions

Given the demonstrated efficacy, these reconstruction methodologies are poised for broader application across diverse spectroscopic surveys, including but not limited to, forthcoming consignments like Dark Energy Spectroscopic Instrument (DESI) and Euclid. Bridging this understanding to higher redshifts will catalyze further refinement of cosmic expansion models and the intrinsic nature of dark energy.

In summary, this paper contributes substantially to improving cosmic distance accuracy, crucial for cosmological parameter estimation, further fortifying the observational cosmology framework. Its legacy will likely extend into influencing survey strategies and methodologies in future cosmic mapping endeavors.