The Effect of Systematic Redshift Biases in BAO Cosmology

TL;DR

This study assesses how small systematic redshift biases affect BAO measurements and cosmological parameter constraints, finding such biases are unlikely to cause significant errors in current or future surveys.

Contribution

The paper provides a quantitative analysis of redshift bias impacts on BAO and introduces a theoretical model predicting these effects, validated against mock survey data.

Findings

Systematic redshift biases have negligible impact on H0 and Ωm constraints.

A theoretical model accurately predicts the impact of uniform redshift systematics.

Biases must be an order of magnitude larger to cause significant parameter shifts.

Abstract

With the remarkable increase in scale and precision provided by upcoming galaxy redshift surveys, systematic errors that were previously negligible may become significant. In this paper, we explore the potential impact of low-magnitude systematic redshift offsets on measurements of the Baryon Acoustic Oscillation (BAO) feature, and the cosmological constraints recovered from such measurements. Using 500 mock galaxy redshift surveys as our baseline sample, we inject a series of systematic redshift biases (ranging from +/-0.2% to +/-2%), and measure the resulting shift in the recovered isotropic BAO scale. When BAO measurements are combined with CMB constraints (in both {\Lambda}CDM and wCDM cosmologies), plausible systematics introduce a negligible offset on combined fits of H0 and {\Omega}m, and systematics must be an order of magnitude greater than this plausible baseline to introduce a 1-{\sigma} shift on such combined fits. We conclude that systematic redshift biases are very unlikely to bias constraints on parameters such as H0 provided by BAO cosmology, either now or in the near future. We also detail a theoretical model that predicts the impact of uniform redshift systematics on {\alpha}, and show this model is in close alignment with the results of our mock survey analysis.