The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements from CMASS anisotropic galaxy clustering

TL;DR

Using the DR12 CMASS sample, the paper measures $D_A(0.59)r_{s,fid}/r_s$, $H(0.59)r_s/r_{s,fid}$, $f(0.59)\sigma_8(0.59)$, and $Ω_m h^2$ from quasi-linear, configuration-space anisotropic clustering. The analysis employs a perturbative model for redshift-space distortions, incorporating BAO dewiggling and a polynomial model for systematics, validated with 2000 MD-PATCHY mocks. The fiducial results are $D_A(0.59)r_{s,fid}/r_s = 1427 \pm 26$ Mpc, $H(0.59)r_s/r_{s,fid} = 97.3 \pm 3.3$ km s$^{-1}$ Mpc$^{-1}$, $f(0.59)\sigma_8(0.59)=0.488 \pm 0.060$, and $Ω_m h^2=0.135 \pm 0.016$, with derived $D_V(0.59)r_{s,fid}/r_s$. When combined with Planck CMB data under ΛCDM (and related models), the results are consistent with a flat universe and a cosmological constant, demonstrating the value of CMASS clustering as a single-probe cosmological constraint.

Abstract

With the largest spectroscopic galaxy survey volume drawn from the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS), we can extract cosmological constraints from the measurements of redshift and geometric distortions at quasi-linear scales (e.g. above 50 $h^{-1}$Mpc). We analyze the broad-range shape of the monopole and quadrupole correlation functions of the BOSS Data Release 12 (DR12) CMASS galaxy sample, at the effective redshift $z=0.59$, to obtain constraints on the Hubble expansion rate $H(z)$, the angular-diameter distance $D_A(z)$, the normalized growth rate $f(z)σ_8(z)$, and the physical matter density $Ω_mh^2$. We obtain robust measurements by including a polynomial as the model for the systematic errors, and find it works very well against the systematic effects, e.g., ones induced by stars and seeing. We provide accurate measurements $\{D_A(0.59)r_{s,fid}/r_s$ $\rm Mpc$, $H(0.59)r_s/r_{s,fid}$ $km s^{-1} Mpc^{-1}$, $f(0.59)σ_8(0.59)$, $Ω_m h^2\}$ = $\{1427\pm26$, $97.3\pm3.3$, $0.488 \pm 0.060$, $0.135\pm0.016\}$, where $r_s$ is the comoving sound horizon at the drag epoch and $r_{s,fid}=147.66$ Mpc is the sound scale of the fiducial cosmology used in this study. The parameters which are not well constrained by our galaxy clustering analysis are marginalized over with wide flat priors. Since no priors from other data sets, e.g., cosmic microwave background (CMB), are adopted and no dark energy models are assumed, our results from BOSS CMASS galaxy clustering alone may be combined with other data sets, i.e., CMB, SNe, lensing or other galaxy clustering data to constrain the parameters of a given cosmological model. The uncertainty on the dark energy equation of state parameter, $w$, from CMB+CMASS is about 8 per cent. The uncertainty on the curvature fraction, $Ω_k$, is 0.3 per cent. We do not find deviation from flat $Λ$CDM.

Figures (11)

• Figure 1: Measurement of effective monopole (left) and quadrupole (right) of the correlation function from the BOSS DR12 CMASS galaxy sample with/without systematics weights for star and seeing(black/red points), compared to the theoretical models given the parameters measured (solid lines). The error bars are the square roots of the diagonal elements of the covariance matrix. In this study, our fitting scale ranges are $55h^{-1}$Mpc $<s<200h^{-1}$Mpc; the bin size is $5h^{-1}$Mpc. The minimum $\chi^2$ per degree of freedom is 0.95 for the correlation function computed including the systematics weights; the one without including the systematics weights is 1.05.
• Figure 2: 2D marginalized contours for $68\%$ and $95\%$ confidence levels for $\Omega_m$ and $H_0$ ($\Lambda$CDM model assumed) from Planck-only (green), Planck+CMASS (red), and Planck+CMASS without including systematics weights (blue).
• Figure 3: 2D marginalized contours for $68\%$ and $95\%$ confidence level for $\Omega_m$ and $\Omega_k$ (o$\Lambda$CDM model assumed) from Planck-only (green), Planck+CMASS (red), and Planck+CMASS without including systematics weights (blue). One can see that $\Omega_k$ is consistent with 0 which is corresponding to the flat universe.
• Figure 4: 2D marginalized contours for $68\%$ and $95\%$ confidence level for $\Omega_m$ and $w$ ($w$CDM model assumed) from Planck-only (green), Planck+CMASS (red), and Planck+CMASS without including systematics weights (blue). One can see that $w$ is consistent with -1 which is corresponding to the $\Lambda$CDM.
• Figure 5: 2D marginalized contours for $68\%$ and $95\%$ confidence level for $\Omega_k$ and $w$ ($w$CDM model assumed) from Planck-only (green), Planck+CMASS (red), and Planck+CMASS without including systematics weights (blue). One can see that $\Omega_k$ is consistent with 0 and $w$ is consistent with -1 which is corresponding to the $\Lambda$CDM.