The Zeldovich approximation and wide-angle redshift-space distortions

TL;DR

This paper calculates wide-angle redshift-space distortion effects using the Zeldovich approximation, improving accuracy over linear theory for upcoming galaxy surveys and revealing significant impacts on BAO measurements.

Contribution

It provides the first calculation of wide-angle terms within the Zeldovich approximation, extending analysis beyond linear perturbation theory.

Findings

Wide angle effects can reach tens of percent of the total signal at low redshift.

Wide angle effects cause slight shifts in the Baryon Acoustic Oscillation scale.

The paper compares different line-of-sight definitions and their impact on measurements.

Abstract

The contribution of line-of-sight peculiar velocities to the observed redshift of objects breaks the translational symmetry of the underlying theory, modifying the predicted 2-point functions. These `wide angle effects' have mostly been studied using linear perturbation theory in the context of the multipoles of the correlation function and power spectrum. In this work we present the first calculation of wide angle terms in the Zeldovich approximation, which is known to be more accurate than linear theory on scales probed by the next generation of galaxy surveys. We present the exact result for dark matter and perturbatively biased tracers as well as the small angle expansion of the configuration- and Fourier-space two-point functions and the connection to the multi-frequency angular power spectrum. We compare different definitions of the line-of-sight direction and discuss how to translate between them. We show that wide angle terms can reach tens of percent of the total signal in a measurement at low redshift in some approximations, and that a generic feature of wide angle effects is to slightly shift the Baryon Acoustic Oscillation scale.