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

TL;DR

This work delivers a high-precision, anisotropic BAO analysis of the final BOSS DR12 data in Fourier space, leveraging density-field reconstruction and a rigorous window-function treatment. By fitting monopole and quadrupole power spectra with a physically motivated model and validating against extensive mock catalogues and N-body tests, the authors extract independent constraints on $D_A(z)$ and $H(z)$ (and isotropic $D_V(z)$) across three redshift bins, achieving percent-level precision and $\sim$8σ detections post-reconstruction. The results are in good agreement with Planck ΛCDM predictions and provide a cornerstone for the final BOSS cosmology constraints released in Alam et al. 2016. The methodology—comprising an exact window-function treatment, robust covariance estimation from mocks, and reconstruction—sets a standard for future BAO analyses in wide-field redshift surveys.

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 $8σ$ (post-reconstruction) for each of the three redshift bins. Our results are in good agreement with the Planck prediction within $Λ$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.

Figures (15)

• Figure 1: BOSS DR12 power spectra in the North Galactic Cap (NGC) for the three redshift bins used in this analysis. The panels in the top row show the power spectra before density field reconstruction, while the bottom row displays the power spectra after density field reconstruction. The blue line indicates the mean of the $2045$ (pre-recon) and $996$ (post-recon) MultiDark-Patchy mock catalogues, while the blue shaded area shows the r.m.s. between them. The errors on the data points are the diagonal of the covariance matrix.
• Figure 2: BOSS DR12 power spectra in the South Galactic Cap (SGC) for the three redshift bins used in this analysis. The panels in the top row show the power spectra before density field reconstruction, while the bottom row displays the power spectra after density field reconstruction. The blue line indicates the mean of the $2048$ (pre-recon) and $999$ (post-recon) MultiDark-Patchy mock catalogues, while the blue shaded area shows the r.m.s. between them. The errors on the data points are the diagonal of the covariance matrix.
• Figure 3: Window function monopole and quadrupole for the three redshift bins of BOSS DR12 as given in eq. \ref{['eq:Well']} and used for the convolved correlation functions in eq. \ref{['eq:conv1']} and \ref{['eq:conv2']}. As expected, the NGC window function extends to larger scales, because of the larger volume of the NGC compared to the SGC.
• Figure 4: Correlation matrix before (top) and after (bottom) density field reconstruction for the North Galactic Cap (NGC) in the three redshift bins used in this analysis. The matrices include the monopole (bottom left corner) and quadrupole (top right corner) as well as their correlation (top left and bottom right). The pre-reconstruction matrices contain $2045$ mock catalogues, while the post-reconstruction results contain $996$ mock catalogues. The colour indicates the level of correlation, with red corresponding to $100\%$ correlation and magenta corresponding to $-25\%$ anti-correlation (there are not many fields lower than $-25\%$). After reconstruction there is less correlation between different $k$ modes and between the multipoles.
• Figure 5: Correlation matrix before (top) and after (bottom) density field reconstruction for the South Galactic Cap (SGC) in the three redshift bins used in this analysis. The matrices include the monopole (bottom left corner) and quadrupole (top right corner) as well as their correlation (top left and bottom right). The pre-reconstruction matrices contain $2048$ mock catalogues, while the post-reconstruction results contain $999$ mock catalogues. The colour indicates the level of correlation, with red corresponding to $100\%$ correlation and magenta corresponding to $-25\%$ anti-correlation (there are not many fields lower than $-25\%$). After reconstruction there is less correlation between different $k$ modes and between the multipoles.