# KiDS-450: Tomographic Cross-Correlation of Galaxy Shear with {\it Planck} Lensing

## TL;DR

This paper presents the first tomographic cross-correlation analysis between galaxy lensing from KiDS-450 and CMB lensing from Planck, validating cosmological models and shear calibration with results consistent within uncertainties.

## Contribution

It introduces the first tomographic galaxy-CMB lensing cross-correlation analysis using five redshift bins, providing a new validation method for shear calibration and source redshift distributions.

## Key findings

- Results are consistent with KiDS-450 cosmology within 1σ.
- Results are consistent with Planck cosmology within 2σ.
- Intrinsic alignment correction improves agreement.

## Abstract

We present the tomographic cross-correlation between galaxy lensing measured in the Kilo Degree Survey (KiDS-450) with overlapping lensing measurements of the cosmic microwave background (CMB), as detected by Planck 2015. We compare our joint probe measurement to the theoretical expectation for a flat $\Lambda$CDM cosmology, assuming the best-fitting cosmological parameters from the KiDS-450 cosmic shear and Planck CMB analyses. We find that our results are consistent within $1\sigma$ with the KiDS-450 cosmology, with an amplitude re-scaling parameter $A_{\rm KiDS} = 0.86 \pm 0.19$. Adopting a Planck cosmology, we find our results are consistent within $2\sigma$, with $A_{\it Planck} = 0.68 \pm 0.15$. We show that the agreement is improved in both cases when the contamination to the signal by intrinsic galaxy alignments is accounted for, increasing $A$ by $\sim 0.1$. This is the first tomographic analysis of the galaxy lensing -- CMB lensing cross-correlation signal, and is based on five photometric redshift bins. We use this measurement as an independent validation of the multiplicative shear calibration and of the calibrated source redshift distribution at high redshifts. We find that constraints on these two quantities are strongly correlated when obtained from this technique, which should therefore not be considered as a stand-alone competitive calibration tool.