kSZ for everyone: the pseudo-Cl approach to stacking

TL;DR

This paper introduces a harmonic-space estimator for the kSZ effect and galaxy momentum cross-correlation, offering practical advantages over traditional stacking by enabling efficient, accurate, and comprehensive analysis of the data.

Contribution

The paper presents a new harmonic-space estimator for kSZ-galaxy cross-correlation that simplifies computation and improves information recovery compared to traditional stacking methods.

Findings

Estimator recovers all information in the galaxy-kSZ cross-correlation.

Allows accurate estimation of statistical uncertainties, including correlations.

Reconstructs standard kSZ stacking measurements with lower computational cost.

Abstract

We present a harmonic-space estimator for the cross-correlation between the kinematic Sunyaev-Zel'dovich effect and the reconstructed galaxy momentum field that offers several practical advantages over the traditional stacking approach. The estimator is easy to deploy using relatively modest computational resources and recovers all information available in the galaxy-kSZ cross-correlation. In particular, by using well-understood power spectrum estimation techniques, its statistical uncertainties, including potential correlated uncertainties with other large-scale structure observables, can be easily and accurately estimated. Moreover, standard kSZ stacking measurements can be reconstructed exactly from the estimator at a lower computational cost, employing harmonic-space, catalog-level techniques to recover all small-scale information.