The redshift-space galaxy two-point correlation function and baryon acoustic oscillations

TL;DR

This paper analyzes the anisotropies in the redshift-space galaxy two-point correlation function related to baryon acoustic oscillations, revealing their dependence on measurement methods and implications for cosmology.

Contribution

It provides a detailed derivation of the anisotropies in the 2PCF using the streaming model and shows how different peak extraction methods affect anisotropy measurements.

Findings

BAO peaks are anisotropic even in linear theory.

Peak extraction method influences the degree of anisotropy observed.

Subtracting broadband tilt enhances the BAO bump along the line of sight.

Abstract

Future galaxy surveys will measure baryon acoustic oscillations (BAOs) with high significance, and a complete understanding of the anisotropies of BAOs in redshift space will be important to exploit the cosmological information in BAOs. Here we describe the anisotropies that arise in the redshift-space galaxy two-point correlation function (2PCF) and elucidate the origin of features that arise in the dependence of the BAOs on the angle between the orientation of the galaxy pair and the line of sight. We do so with a derivation of the configuration-space 2PCF using streaming model. We find that, contrary to common belief, the locations of BAO peaks in the redshift-space 2PCF are anisotropic even in the linear theory. Anisotropies in BAO depend strongly on the method of extracting the peak, showing maximum 3 % angular variation. We also find that extracting the BAO peak of $r^2\xi(r,\mu)$ significantly reduces the anisotropy to sub-percent level angular variation. When subtracting the tilt due to the broadband behavior of the 2PCF, the BAO bump is enhanced along the line of sight because of local infall velocities toward the BAO bump. Precise measurement of the angular dependence of the redshift-space 2PCF will allow new geometrical tests of dark energy beyond the BAO.