A method to extract the redshift distortions beta parameter in configuration space from minimal cosmological assumptions

TL;DR

This paper introduces a new method to measure the redshift-space distortion parameter beta using observed correlation functions, minimizing cosmological assumptions and reducing systematic errors.

Contribution

The method uniquely combines monopole and quadrupole correlation functions to accurately extract beta without relying on theoretical correlation functions or bias assumptions.

Findings

Achieves a few percent error on beta with large surveys

Removes impact of non-linearities and redshift errors effectively

Identifies a baryonic feature that may affect growth measurements

Abstract

We present a method to extract the redshift-space distortions beta parameter in configuration space with a minimal set of cosmological assumptions. We show that a novel combination of the observed monopole and quadrupole correlation functions can remove efficiently the impact of mild non linearities and redshift errors. The method offers a series of convenient properties: it does not depend on the theoretical linear correlation function, the mean galaxy density is irrelevant, only convolutions are used, there is no explicit dependence on linear bias. Analyses based on dark matter N-body simulations and Fisher matrix demonstrate that errors of a few percent on beta are possible with a full sky, 1(Gpc/h)^3 survey centered at a redshift of unity and with negligible shot noise. We also find a baryonic feature in the normalized quadrupole in configuration space that should complicate the extraction of the growth parameter from the linear theory asymptote, but that does not have a major impact with our method.