The clustering of galaxies in the SDSS-III Baryon Oscillation Spectroscopic Survey: single-probe measurements and the strong power of normalized growth rate on constraining dark energy

TL;DR

This paper measures galaxy clustering from SDSS-III BOSS to constrain cosmological parameters, emphasizing the significant role of the normalized growth rate in dark energy studies without relying on external priors.

Contribution

It provides single-probe measurements of galaxy clustering and highlights the importance of including the normalized growth rate for constraining dark energy.

Findings

Measured H(z), D_A(z), and f(z)σ_8(z) at z=0.57 with uncertainties.

Showed that including f(z)σ_8(z) greatly enhances dark energy constraints.

Combined results with CMB data to estimate dark energy equation of state w=-0.90±0.11.

Abstract

We present measurements of the anisotropic galaxy clustering from the Data Release 9 (DR9) CMASS sample of the SDSS-III Baryon Oscillation Spectroscopic Survey (BOSS). We analyze the broad-range shape of the monopole and quadrupole correlation functions to obtain constraints, at the effective redshift $z=0.57$ of the sample, on the Hubble expansion rate $H(z)$, the angular-diameter distance $D_A(z)$, the normalized growth rate $f(z)\sigma_8(z)$, the physical matter density $\Omega_m h^2$, and the biased amplitude of matter fluctuation b\sigma_8(z). We obtain {$H(0.57)$, $D_A(0.57)$, $f(0.57)\sigma_8(0.57)$, $\Omega_m h^2$, $b\sigma_8(0.57)$} = {$87.6_{-6.8}^{+6.7}$, $1396\pm73$, $0.126_{-0.010}^{+0.008}$, $1.19\pm0.14$, $0.428\pm0.066$} and their covariance matrix as well. The parameters which are not well constrained by our of galaxy clustering analysis are marginalized over with wide flat priors. Since no priors from other data sets (i.e., 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. We show that the major power on constraining dark energy from the anisotropic galaxy clustering signal, as compared to the angular-averaged one (monopole), arises from including the normalized growth rate $f(z)\sigma_8(z)$. In the case of the wCDM cosmological model our single-probe CMASS constraints, combined with CMB (WMAP9+SPT), yield a value for the dark energy equation of state parameter of $w=-0.90\pm0.11$. Therefore, it is important to include $f(z)\sigma_8(z)$ while investigating the nature of dark energy with current and upcoming large-scale galaxy surveys.