The Baryonic Acoustic Feature and Large-Scale Clustering in the SDSS LRG Sample

TL;DR

This paper analyzes the large-scale clustering of SDSS LRGs, detecting the baryonic acoustic feature and constraining cosmological parameters, with results consistent with LCDM and previous studies.

Contribution

It provides a detailed measurement of the baryonic acoustic peak in the SDSS LRG sample and compares it with theoretical models, confirming the standard cosmological model.

Findings

The baryonic acoustic peak is detected at s_p=103.6 Mpc/h.

The measured r_s/D_V ratio is 0.1394, consistent with previous results.

Systematic effects are smaller than sample variance.

Abstract

We examine the correlation function \xi of the Sloan Digital Sky Survey (SDSS) Luminous Red Galaxy sample (LRG) at large scales (60<s<400 Mpc/h) using the final data release (DR7; 105,831 LRGs between 0.16<z<0.47). Using mock catalogs, we demonstrate that the observed baryonic acoustic peak and larger scale signal are consistent with LCDM at the 1.5\sigma level. The signal at 155<s<200 Mpc/h tends to be high relative to theoretical expectations; this slight deviation can be attributed to a bright subsample of the LRGs. Fitting data to a non-linear, redshift-space, template based-model, we constrain the peak position at s_p=103.6+3.6-2.4 Mpc/h when fitting the range 60<s<150 Mpc/h (1\sigma uncertainties measured from the mocks. This redshift-space distance s_p is related to the comoving sound horizon scale r_s after taking into account matter clustering non-linearities, redshift distortions and galaxy clustering bias. Mock catalogs show that the probability that a DR7-sized sample would not have an identifiable peak is at least 10%. As a consistency check of a fiducial cosmology, we use the observed s_p to obtain the distance D_V=[(1+z)^2D_A^2cz/H(z)]^(1/3) relative to the acoustic scale. We find r_s/D_V(z=0.278)=0.1394+-0.0049. This result is in excellent agreement with Percival et. al (2009), who examine roughly the same data set, but using the power spectrum. Comparison with other determinations in the literature are also in very good agreement. We have tested our results against a battery of possible systematic effects, finding all effects are smaller than our estimated sample variance.