Large-Scale Anisotropic Correlation Function of SDSS Luminous Red Galaxies

Abstract

We study the large-scale anisotropic two-point correlation function using 46,760 luminous red galaxies at redshifts 0.16 -- 0.47 from the Sloan Digital Sky Survey. We measure the correlation function as a function of separations parallel and perpendicular to the line-of-sight in order to take account of anisotropy of the large-scale structure in redshift space. We find a slight signal of baryonic features in the anisotropic correlation function, i.e., a ``baryon ridge'' which corresponds to a baryon acoustic peak in the spherically averaged correlation function which has already been reported using the same sample. The baryon ridge has primarily a spherical structure with a known radius in comoving coordinates. It enables us to divide the redshift distortion effects into dynamical and geometrical components and provides further constraints on cosmological parameters, including the dark energy equation-of-state. With an assumption of a flat $Λ$ cosmology, we find the best-fit values of $Ω_{\rm m} = 0.218^{+0.047}_{-0.037}$ and $Ω_{\rm b} = 0.047^{+0.016}_{-0.016}$ (68% C.L.) when we use the overall shape of the anisotropic correlation function of $40<s<200\himpc$ including a scale of baryon acoustic oscillations. When an additional assumption $Ω_{\rm b}h^2=0.024$ is adopted, we obtain $Ω_{\rm DE}=0.770^{+0.051}_{-0.040}$ and $w=-0.93^{+0.45}_{-0.35}$. These constraints are estimated only from our data of the anisotropic correlation function, and they agree quite well with values both from the cosmic microwave background (CMB) anisotropies and from other complementary statistics using the LRG sample. With the CMB prior from the 3 year WMAP results, we give stronger constraints on those parameters.