Cosmological constraints without fingers of God

TL;DR

This paper introduces a new observable, $Q_0$, that mitigates the impact of fingers of God in redshift-space distortions, enabling more accurate cosmological constraints from galaxy clustering data.

Contribution

The authors propose and validate a new statistic, $Q_0$, which is unaffected by fingers of God and allows perturbation theory to be applied more effectively in redshift space.

Findings

$Q_0$ can be accurately modeled with perturbation theory up to $k_{max} \\simeq 0.4~h~Mpc^{-1}$.

Using $Q_0$ improves cosmological parameter constraints by 10% to 100%.

The method is validated with simulations and BOSS data.

Abstract

Non-linear redshift-space distortions ("fingers of God") are challenging to model analytically, a fact that limits the applicability of perturbation theory in redshift space as compared to real space. We show how this problem can be mitigated using a new observable, $Q_0$, which can be easily estimated from the redshift space clustering data and is approximately equal to the real space power spectrum. The new statistic does not suffer from fingers of God and can be accurately described with perturbation theory down to $k_{\rm max}\simeq 0.4~h~\text{Mpc}^{-1}$. It can be straightforwardly included in the likelihood at negligible additional computational cost, and yields noticeable improvements on cosmological parameters compared to standard power spectrum multipole analyses. Using both simulations and observational data from the Baryon Oscillation Spectroscopic Survey, we show that improvements vary from $10\%$ to $100\%$ depending on the cosmological parameter considered, the galaxy sample and the survey volume.