Pairwise kSZ signal extraction efficacy and optical depth estimation

TL;DR

This paper evaluates methods for extracting the pairwise kSZ signal from galaxy cluster data, demonstrating that aperture photometry and matched filter techniques can unbiasedly estimate the optical depth, aiding future cosmological studies.

Contribution

It introduces calibrated aperture photometry and matched filter approaches for unbiased kSZ signal and optical depth estimation from survey data, validated with simulations and ACT data.

Findings

Both methods recover unbiased kSZ signals.

Optical depth estimates align with thermal SZ measurements.

Techniques are applicable to upcoming surveys like CMB-S4.

Abstract

We determine the efficacy of the kinematic Sunyaev-Zel'dovich signal extraction pipeline, using pairwise kSZ measurements, in recovering unbiased estimates of the signal and inference of the associated optical depth. We consider the impact of cluster co-alignments along the line of sight, the modeling of baryonic clustering, and the presence of diffuse gas, as well as instrument beam convolution and noise. We demonstrate that two complementary approaches, aperture photometry, and a matched filter, can be used to recover an unbiased estimate of the cluster kSZ signal and the associated optical depth. Aperture photometry requires a correction factor accounting for the subtraction of signal in the annulus while the matched filter requires a tuning of the signal template profile. We show that both of these can be calibrated from simulated survey data. The optical depth estimates are also consistent with those inferred from stacked thermal SZ measurements. We apply the approaches to the publicly available Atacama Cosmology Telescope (ACT) data. The techniques developed here provide a promising method to leverage upcoming kSZ measurements, from ACT, Simons Observatory, CCAT, and CMB-S4 with spectroscopic galaxy surveys from DESI, Euclid, and Roman, to constrain cosmological properties of the dark energy, gravity, and neutrino masses.