Cosmological constraints from baryon acoustic oscillations and clustering of large-scale structure

TL;DR

This study conducts joint cosmological parameter fits using BAO positions and broader large-scale structure (LSS) clustering data across redshifts $0.1<z<2.4$, without relying on CMB priors for the standard ruler. It finds that BAO-position alone constrain $Ω_m$ and $w$, while incorporating LSS shape, Alcock-Paczynski, and growth-rate information tightens parameters to $Ω_m\approx0.29$, $H_0\approx67.5$ km s$^{-1}$ Mpc$^{-1}$, and $σ_8\approx0.80$ for ΛCDM, with $w\approx-1.14$ in $w$CDM. The combined CMB+BAO+LSS constraint yields $w\approx-1.03\pm0.06$, consistent with ΛCDM, though allowing $w<-1$ can reduce tensions with some data while increasing tension with $σ_8$ from growth rates. The results illustrate the power and consistency of low-redshift BAO/LSS probes as complementary to CMB data and highlight the importance of future high-precision LSS and Ly-$\alpha$ measurements for constraining dark energy and curvature.

Abstract

We constrain cosmological parameters using combined measurements of the baryon acoustic oscillation (BAO) feature in the correlation function of galaxies and Ly-αabsorbers that together cover 0.1 < z < 2.4. The BAO position measurements alone -- without fixing the absolute sound horizon `standard ruler' length with cosmic microwave background (CMB) data -- constrain Ω_m = 0.303 +/- 0.040 (68 per cent confidence) for a flat ΛCDM model, and w = -1.06^{+0.33}_{-0.32}, Ω_m = 0.292^{+0.045}_{-0.040} for a flat wCDM model. Adding other large-scale structure (LSS) clustering constraints -- correlation function shape, the Alcock-Paczynski test and growth rate information -- to the BAO considerably tightens constraints (Ω_m = 0.290 +/- 0.019, H_0 = 67.5 +/- 2.8 km s^{-1} Mpc^{-1}, σ_8 = 0.80 +/- 0.05 for ΛCDM, and w = -1.14 +/- 0.19 for wCDM). The LSS data mildly prefer a lower value of H_0, and a higher value of Ω_m, than local distance ladder and type IA supernovae (SNe) measurements, respectively. While tension in the combined CMB, SNe and distance ladder data appears to be relieved by allowing w < -1, this freedom introduces tension with the LSS σ_8 constraint from the growth rate of matter fluctuations. The combined constraint on w from CMB, BAO and LSS clustering for a flat wCDM model is w = -1.03 +/- 0.06.

Figures (5)

• Figure 1: $\Lambda$CDM constraints from measurements of BAO position. We show 68.3 and 95.5 per cent confidence contours for the combined BAO data set (Table 1, top), and for the 6dFGS beutler/etal:2011, BOSS CMASS anderson/etal:prep and BOSS Ly-$\alpha$slosar/etal:2013 data separately, to illustrate their complementarity. Constraints from our expanded analysis including other large-scale structure clustering constraints (Table 1, bottom), and CMB constraints from combining Planck, WMAP, ACT and SPT data planckparams:prep are also shown. The BAO, LSS and CMB constraints are in good agreement for the $\Lambda$CDM model.
• Figure 2: Marginalized $H_0$ constraints for the $\Lambda$CDM model. While BAO position measurements alone do not constraint $H_0$, a constraint may be obtained by either adding information from the shape of the large-scale structure correlation function, or adding a prior on the baryon density pettini/cooke:2012. In either case, there is a mild preference for a lower $H_0$ value than the distance ladder measurements, consistent with recent Planck results. Note that the choice of large-scale structure constraints moderately affects this comparison (see text).
• Figure 3: Marginalized two-dimensional constraints from the triplet of parameters $\{w,\Omega_m,H_0\}$ for the $w$CDM model. We compare results from the BAO and LSS clustering analyses in this work with the latest CMB constraints planckparams:prep, the SNLS SNe compilation conley/etal:2011, and local distance ladder $H_0$ measurements riess/etal:2011. Decreasing $w$ below $-1$ appears to relieve the $\Lambda$CDM tension between these data sets when these three parameters are considered -- but see Figure 4.
• Figure 4: Marginalized $\sigma_8$ and $w$ constraints (68.3 and 95.5 per cent confidence) in the $w$CDM model. While tension in the combined CMB, SNe and distance ladder data set is effectively relieved by allowing $w<-1$ (Figure 3), the resulting $\sigma_8$ constraint is in moderate tension with the large-scale structure growth rate constraints from redshift-space distortion measurements. Note that the CMB and LSS constraints on $\sigma_8$ are in good agreement for the $\Lambda$CDM model (Table 2); the combined CMB and LSS constraint is $w=-1.03\pm0.06$.
• Figure 5: Comparison of $\Lambda$CDM constraints (68.3 and 95.5 per cent confidence) in the $\sigma_8-\Omega_m$ plane for CMB and several low-redshift data sets. While growth rate information from redshift-space distortions allows LSS clustering measurements to constrain $\sigma_8$, current precision is too low to meaningfully inform the comparison of CMB constraints with those from (for instance) cluster abundance planckclusters:prep or weak lensing shear correlations kilbinger/etal:2012.