The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space (1607.03149v1)

Abstract: We analyse the Baryon Acoustic Oscillation (BAO) signal of the final Baryon Oscillation Spectroscopic Survey (BOSS) data release (DR12). Our analysis is performed in Fourier-space, using the power spectrum monopole and quadrupole. The dataset includes $1\,198\,006$ galaxies over the redshift range $0.2 < z < 0.75$. We divide this dataset into three (overlapping) redshift bins with the effective redshifts $\zeff = 0.38$, $0.51$ and $0.61$. We demonstrate the reliability of our analysis pipeline using N-body simulations as well as $\sim 1000$ MultiDark-Patchy mock catalogues, which mimic the BOSS-DR12 target selection. We apply density field reconstruction to enhance the BAO signal-to-noise ratio. By including the power spectrum quadrupole we can separate the line-of-sight and angular modes, which allows us to constrain the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$ separately. We obtain two independent $1.6\%$ and $1.5\%$ constraints on $D_A(z)$ and $2.9\%$ and $2.3\%$ constraints on $H(z)$ for the low ($\zeff=0.38$) and high ($\zeff=0.61$) redshift bin, respectively. We obtain two independent $1\%$ and $0.9\%$ constraints on the angular averaged distance $D_V(z)$, when ignoring the Alcock-Paczynski effect. The detection significance of the BAO signal is of the order of $8\sigma$ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within $\Lambda$CDM. This paper is part of a set that analyses the final galaxy clustering dataset from BOSS. The measurements and likelihoods presented here are combined with others in~\citet{Alam2016} to produce the final cosmological constraints from BOSS.

• The paper employs density field reconstruction in Fourier space to enhance the BAO signal, achieving an 8σ detection in each redshift bin.
• It refines cosmological parameters by constraining angular diameter distances to around 1.5–1.6% and Hubble parameters to 2.3–2.9% across multiple redshift bins.
• The study’s methodologies set robust benchmarks for future BAO analyses and reinforce the ΛCDM model with high-precision measurements.

Analysis of Baryon Acoustic Oscillations in Fourier Space

The paper "The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: Baryon Acoustic Oscillations in Fourier-space" by Florian Beutler et al. presents a detailed analysis of the Baryon Acoustic Oscillation (BAO) signal using the final data release of the BOSS project (DR12). This research is crucial for understanding the large-scale structure of the Universe and its expansion history.

Overview of Methodology

The paper employs a Fourier-space analysis of the galaxy clustering data from BOSS DR12, which encompasses 1,198,006 galaxies across a redshift range of 0.2 to 0.75. The dataset is partitioned into three overlapping redshift bins with effective redshifts of 0.38, 0.51, and 0.61. The analysis utilizes the power spectrum monopole and quadrupole derived from N-body simulations and over 1000 MultiDark-Patchy mock catalogues to ensure the robustness of the results.

Key to the methodology is the application of density field reconstruction, a technique that enhances the BAO signal-to-noise ratio by reversing the effects of non-linear growth and redshift-space distortions. The inclusion of the power spectrum quadrupole allows the authors to disentangle line-of-sight and angular modes, enabling separate constraints on the angular diameter distance $D_A(z)$ and the Hubble parameter $H(z)$.

Numerical Results

The authors achieve a detection significance of the BAO signal at around $8\sigma$ post-reconstruction for each redshift bin. The analysis yields precise constraints on cosmological parameters: two independent constraints on $D_A(z)$ at 1.6% and 1.5%, and constraints on $H(z)$ at 2.9% and 2.3% for the low and high redshift bins, respectively. Additionally, when neglecting the Alcock-Paczynski effect, the angular averaged distance $D_V(z)$ is constrained at 1% and 0.9%.

Theoretical and Practical Implications

The paper's findings align with the $\Lambda$CDM model and the Planck mission's predictions, reinforcing the current understanding of cosmological models. By providing refined measurements of the Universe's expansion history, this work has far-reaching implications for cosmological theories and can potentially inform the next generation of surveys targeting even finer details of cosmic structure.

In a practical context, the methodologies employed in this paper, such as density field reconstruction in Fourier space and the handling of window functions, set a precedent for future BAO analyses. These techniques ensure robust, high-precision measurements that can be applied in broader cosmological research.

Future Research Directions

Future developments could expand upon this research by exploring the application of these methodologies to other cosmological probes, such as weak lensing surveys or integrated Sachs-Wolfe effect measurements. Additionally, the continuous refinement of BAO detection techniques will undoubtedly be crucial as observational capabilities evolve and datasets grow in both size and complexity.

This paper cements the importance of sophisticated statistical analyses and modeling in understanding fundamental cosmological parameters, utilizing BAO as a "standard ruler" not just for current surveys, but as a foundational tool for future explorations in cosmology.