Redshift-Space Enhancement of Line-of-Sight Baryon Acoustic Oscillations in the SDSS Main-Galaxy Sample

TL;DR

This paper investigates how redshift-space distortions enhance the visibility of baryon acoustic oscillations along the line of sight, using simulations and SDSS data, revealing a sharper BAO feature with increased significance.

Contribution

It demonstrates that redshift-space distortions can sharpen BAO features along the line of sight, and provides observational evidence from SDSS data supporting this effect.

Findings

Redshift-space distortions make BAO features sharper along the line of sight.

A localized BAO bump was detected at approximately 110 Mpc/h with 4 sigma significance.

The probability of such a signal arising from a non-BAO power spectrum is about 0.2%.

Abstract

We show that redshift-space distortions of galaxy correlations have a strong effect on correlation functions with distinct, localized features, like the signature of the baryon acoustic oscillations (BAO). Near the line of sight, the features become sharper as a result of redshift-space distortions. We demonstrate this effect by measuring the correlation function in Gaussian simulations and the Millennium Simulation. We also analyze the SDSS DR7 main-galaxy sample (MGS), splitting the sample into slices 2.5 degrees on the sky in various rotations. Measuring 2D correlation functions in each slice, we do see a sharp bump along the line of sight. Using Mexican-hat wavelets, we localize it to (110 +/- 10) Mpc/h. Averaging only along the line of sight, we estimate its significance at a particular wavelet scale and location at 2.2 sigma. In a flat angular weighting in the (pi,r_p) coordinate system, the noise level is suppressed, pushing the bump's significance to 4 sigma. We estimate that there is about a 0.2% chance of getting such a signal anywhere in the vicinity of the BAO scale from a power spectrum lacking a BAO feature. However, these estimates of the significances make some use of idealized Gaussian simulations, and thus are likely a bit optimistic.