Regarding the Line-of-Sight Baryonic Acoustic Feature in the Sloan Digital Sky Survey and Baryon Oscillation Spectroscopic Survey Luminous Red Galaxy Samples

TL;DR

This study investigates the line-of-sight baryonic acoustic feature in SDSS LRG samples, finding no convincing evidence of its detection and assessing its potential observability in future BOSS data.

Contribution

The paper provides a detailed analysis of the line-of-sight baryonic acoustic feature, showing that previous strong signals can be explained by noise and modeling, and evaluates its detectability in upcoming surveys.

Findings

No convincing evidence of the line-of-sight BAO feature in SDSS LRG data.

Mock catalogs suggest the feature is unlikely to be detected in BOSS with narrow angular cuts.

Wider angular cuts can improve the comparison of line-of-sight and transverse distances.

Abstract

We analyze the line-of-sight baryonic acoustic feature in the two-point correlation function {\xi} of the Sloan Digital Sky Survey (SDSS) luminous red galaxy (LRG) sample (0.16 < z < 0.47). By defining a narrow line-of-sight region, rp < 5.5 Mpc/h, where rp is the transverse separation component, we measure a strong excess of clustering at ~ 110 Mpc/h, as previously reported in the literature. We also test these results in an alternative coordinate system, by defining the line-of-sight as {\theta} < 3{\deg}, where {\theta} is the opening angle. This clustering excess appears much stronger than the feature in the better-measured monopole. A fiducial {\Lambda}CDM non-linear model in redshift-space predicts a much weaker signature. We use realistic mock catalogs to model the expected signal and noise. We find that the line-of-sight measurements can be explained well by our mocks as well as by a featureless {\xi} = 0. We conclude that there is no convincing evidence that the strong clustering measurement is the line-of-sight baryonic acoustic feature. We also evaluate how detectable such a signal would be in the upcoming Baryon Oscillation Spectroscopic Survey LRG volume (BOSS). Mock LRG catalogs (z < 0.6) suggest that: (i) the narrow line- of-sight cylinder and cone defined above probably will not reveal a detectable acoustic feature in BOSS; (ii) a clustering measurement as high as that in the current sample can be ruled out (or confirmed) at a high confidence level using a BOSS-sized data set; and (iii) an analysis with wider angular cuts, which provide better signal-to-noise ratios, can nevertheless be used to compare line-of-sight and transverse distances, and thereby constrain the expansion rate H(z) and diameter distance DA(z).