Strong detection of the CMB lensingxgalaxy weak lensingcross-correlation from ACT-DR4,PlanckLegacy and KiDS-1000

TL;DR

This paper measures the cross-correlation between galaxy weak lensing from KiDS-1000 and CMB lensing from ACT and Planck, achieving high significance detections and providing independent constraints on cosmological parameters and redshift calibration.

Contribution

It presents the first high-significance detection of CMB-weak lensing cross-correlation using KiDS-1000, ACT, and Planck data, and demonstrates its utility for cosmological constraints and redshift calibration.

Findings

Cross-correlation detection significance of 7.7σ for combined samples.

Consistent cosmological constraints with Planck and KiDS-1000 models.

Independent validation of redshift calibration at high redshift.

Abstract

We measure the cross-correlation between galaxy weak lensing data from the Kilo Degree Survey (KiDS-1000, DR4) and cosmic microwave background (CMB) lensing data from the Atacama Cosmology Telescope (ACT, DR4) and the Planck Legacy survey. We use two samples of source galaxies, selected with photometric redshifts, $(0.1<z_{\rm B}<1.2)$ and $(1.2<z_{\rm B}<2)$, which produce a combined detection significance of the CMB lensing/weak galaxy lensing cross-spectrum of $7.7\sigma$. With the lower redshift galaxy sample, for which the cross-correlation is detected at a significance of $5.3\sigma$, we present joint cosmological constraints on the matter density parameter, $\Omega_{\rm m}$, and the matter fluctuation amplitude parameter, $\sigma_8$, marginalising over three nuisance parameters that model our uncertainty in the redshift and shear calibration, and the intrinsic alignment of galaxies. We find our measurement to be consistent with the best-fitting flat $\Lambda$CDM cosmological models from both Planck and KiDS-1000. We demonstrate the capacity of CMB-weak lensing cross-correlations to set constraints on either the redshift or shear calibration, by analysing a previously unused high-redshift KiDS galaxy sample $(1.2<z_{\rm B}<2)$, with the cross-correlation detected at a significance of $7\sigma$. This analysis provides an independent assessment for the accuracy of redshift measurements in a regime that is challenging to calibrate directly owing to known incompleteness in spectroscopic surveys.