Gravitational Lensing Effects on the Baryonic Acoustic Oscillation Signature in the Redshift-Space Correlation Function

TL;DR

Gravitational lensing introduces minor but measurable shifts in the BAO peak in galaxy correlation functions, which vary with redshift and line-of-sight angle, but can be modeled and corrected for precise cosmological measurements.

Contribution

This paper quantifies the impact of gravitational lensing on BAO measurements and demonstrates that lensing effects can be separated and corrected, improving dark energy and curvature constraints.

Findings

Lensing causes a peak shift of 10^-4 at z=1, increasing to 10^-3 at z=2.5.

Effects are stronger near the line-of-sight but remain small.

Lensing contribution can be measured and subtracted from data.

Abstract

Measurements of the baryonic acoustic oscillation (BAO) peak in the redshift-space correlation function yield the angular diameter distance D_A(z) and the Hubble parameter H(z) as a function of redshift, constraining the properties of dark energy and space curvature. We discuss the perturbations introduced in the galaxy correlation function by gravitational lensing through the effect of magnification bias and its cross-correlation with the galaxy density. At the BAO scale, gravitational lensing adds a small and slowly varying component to the galaxy correlation function and does not change its shape significantly, through which the BAO peak is measured. The relative shift in the position of the BAO peak caused by gravitational lensing in the angle-averaged correlation function is 10^-4 at z=1, rising to 10^-3 at z=2.5. Lensing effects are stronger near the line-of-sight, however the relative peak shift increases only to 10^-3.3 and 10^-2.4 at z=1 and z=2.5, when the galaxy correlation is averaged within 5 degrees of the line-of-sight (containing only 0.4% of the galaxy pairs in a survey). Furthermore, the lensing contribution can be measured separately and subtracted from the observed correlation at the BAO scale.