CMB lensing tomography , or the cross-correlation between CMB lensing maps and large-scale structure tracers over a well-defined redshift range , has the potential to map the amplitude and growth of structure over cosmic time , provide some of the most stringent tests of gravity , and break important degeneracies between cosmological parameters .
In this work , we use the unWISE galaxy catalog to provide three samples at median redshifts z \sim 0.6 , 1.1 and 1.5 , fully spanning the Dark Energy dominated era , together with the most recent Planck CMB lensing maps .
We obtain a combined cross-correlation significance S / N = 58.7 over the range of scales 300 < \ell < 1000 .
We measure the redshift distribution of unWISE sources by a combination of cross-matching with the COSMOS photometric catalog and cross-correlation with BOSS galaxies and quasars and eBOSS quasars .
We also show that magnification bias must be included in our analysis and perform a number of null tests .
In a companion paper , we explore the derived cosmological parameters by modeling the non-linearities and propagating the redshift distribution uncertainties .