The clustering of galaxies in the completed SDSS-III Baryon Oscillation Spectroscopic Survey: cosmological implications of the configuration-space clustering wedges

TL;DR

This work analyzes the final BOSS DR12 galaxy sample using anisotropic clustering in configuration space, focusing on three clustering wedges to extract both the expansion history and growth of structure. It introduces a state-of-the-art model that combines non-linear dynamics via gRPT, galaxy bias, and redshift-space distortions, validated against extensive N-body and mock tests, and applies Alcock-Paczynski scaling to interpret the data. By combining Planck CMB measurements and SN data, the study derives tight constraints on the $\Lambda$CDM parameter space and extensions, finding results consistent with a flat, cosmological-constant universe and GR predictions, e.g., $w_{DE}=-0.996\pm0.042$, $\Omega_k=-0.0007\pm0.0030$, $\sum m_ν<0.25$ eV, and $\gamma=0.609\pm0.079$. The clustering wedges provide compressed, robust probes ($D_V(z)/r_d$, $F_{AP}(z)$, $f\sigma_8(z)$) that agree with Planck-derived expectations, highlighting anisotropic clustering as a powerful cosmological tool for current and future surveys.

Abstract

We explore the cosmological implications of anisotropic clustering measurements in configuration space of the final galaxy samples from Data Release 12 of the SDSS-III Baryon Oscillation Spectroscopic Survey. We implement a new detailed modelling of the effects of non-linearities, galaxy bias and redshift-space distortions that can be used to extract unbiased cosmological information from our measurements for scales $s \gtrsim 20\,h^{-1}{\rm Mpc}$. We combined the galaxy clustering information from BOSS with the latest cosmic microwave background (CMB) observations and Type Ia supernovae samples and found no significant evidence for a deviation from the $Λ$CDM cosmological model. In particular, these data sets can constrain the dark energy equation of state parameter to $w_{\rm DE}=-0.996\pm0.042$ when assumed time-independent, the curvature of the Universe to $Ω_{k}=-0.0007\pm 0.0030$ and the sum of the neutrino masses to $\sum m_ν < 0.25\,{\rm eV}$ at 95 per cent CL. We explore the constraints on the growth rate of cosmic structures assuming $f(z)=Ω_{\rm m}(z)^γ$ and obtain $γ= 0.609\pm 0.079$, in good agreement with the predictions of general relativity of $γ=0.55$. We compress the information of our clustering measurements into constraints on the parameter combinations $D_{\rm V}(z)/r_{\rm d}$, $F_{\rm AP}(z)$ and $fσ_8(z)$ at the effective redshifts of $z=0.38$, $0.51$ and $0.61$ with their respective covariance matrices and find good agreement with the predictions for these parameters obtained from the best-fitting $Λ$CDM model to the CMB data from the Planck satellite. 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 Alam et al. (2016) to produce the final cosmological constraints from BOSS.

Figures (16)

• Figure 1: Clustering wedges in the directions parallel (blue) intermediate (green) and transverse (red) to the line of sight measured from the combined galaxy sample of BOSS DR12 in our three redshift bins, as a function of the pair separation expressed in ${\rm Mpc}$ and $h^{-1}{\rm Mpc}$ in the lower and upper axes, respectively. The error bars correspond to the dispersion of the results inferred from a set of $N_{\rm m}=2045$ mock catalogues of the full BOSS survey. The solid lines correspond to the best-fitting model to these measurements obtained as described in Section \ref{['sec:bao']}.
• Figure 2: Mean dark-matter real-space power spectrum of the Minerva simulations at $z = 0.57$ (blue long-dashed lines) compared against the predictions of linear theory (black short-dashed lines), two-loop RPT as implemented in MPTBreeze (orange dot-dashed lines) and one-loop gRPT (red solid lines). The shaded region corresponds to a 2 per cent uncertainty in the value of $P(k)$.
• Figure 3: Mean clustering wedges of the Minerva HOD samples for the two (upper panel) and three (lower panel) $\mu$-bins configurations. The error bars correspond to the square root of the diagonal entries of the covariance matrices computed using the Gaussian recipes of Grieb2016. The solid lines correspond to the model described in Section \ref{['sec:model']}, which gives an excellent description of the simulation results.
• Figure 4: Mean values (points) and 68 per cent CL on $q_{\perp}$, $q_{\parallel}$ and $f\sigma_8$ derived from the measurements of two (squares) and three (circles) clustering wedges from the Minerva HOD galaxy samples as a function of the minimum scale included in the fits. The dashed lines correspond to the true values of these parameters. Based on this test we set a minimum scale of $s_{\rm min}=20\,h^{-1}{\rm Mpc}$ for our fits to the BOSS combined sample clustering wedges.
• Figure 5: Difference between the values of $\alpha_{\perp}$, $\alpha_{\parallel}$ and $f\sigma_8$ obtained from the measurements of two (squares) and three (circles) wedges from each of the HOD boxes (labelled A to G) of the RSD challenge of Tinker2016. The dashed lines correspond to the mean differences over all boxes. The shaded regions indicate the uncertainties associated with the constraints on these parameters inferred from the real BOSS sample (see Section \ref{['sec:bao']}).