BAO Extractor: bias and redshift space effects

TL;DR

This paper introduces a robust method to measure the BAO scale by extracting oscillations from the nonlinear power spectrum, demonstrating high accuracy in simulations and a simple theoretical model that accounts for nonlinear effects.

Contribution

A new procedure to extract the BAO scale directly from the nonlinear power spectrum, improving robustness and accuracy over traditional fitting methods.

Findings

The extracted BAO scale is highly robust and reproducible across models.

Nonlinear effects, redshift space distortions, and halo bias can be modeled with sub-percent accuracy.

A simple IR-based perturbation theory model accurately reproduces BAO measurements without external inputs.

Abstract

We study a new procedure to measure the sound horizon scale via Baryonic Acoustic Oscillations (BAO). Instead of fitting the measured power spectrum (PS) to a theoretical model containing the cosmological informations and all the nonlinear effects, we define a procedure to project out (or to "extract") the oscillating component from a given nonlinear PS. We show that the BAO scale extracted in this way is extremely robust and, moreover, can be reproduced by simple theoretical models at any redshift. By using N-body simulations, we discuss the effect of the nonlinear evolution of the matter field, of redshift space distortions and of scale-dependent halo bias, showing that all these effects can be reproduced with sub-percent accuracy. We give a one-parameter theoretical model based on a simple (IR) modification of 1-loop perturbation theory, which reproduces the BAO scale from measurements of halo clustering in redshift space at better than $0.1\%$ level and does not need any external UV input, such as coefficients measured from N-body simulations.