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