Cosmological constraints from unWISE and Planck CMB lensing tomography

A number of recent, low-redshift, lensing measurements hint at a universe in which the amplitude of lensing is lower than that predicted from the Lambda CDM model fit to the data of the Planck CMB mission. Here we use the auto-and cross-correlation signal of unWISE galaxies and Planck CMB lensing maps to infer cosmological parameters at low redshift. In particular, we consider three unWISE samples (denoted as blue, green and red) at median redshifts z similar to 0.6, 1.1 and 1.5, which fully cover the Dark Energy dominated era. Our cross-correlation measurements, with combined significance S/N similar to 80, are used to infer the amplitude of low-redshift fluctuations, sigma(8); the fraction of matter in the Universe, Omega(m); and the combination S-8 sigma(8)(Omega(m)/0.3)(0.5) to which these low-redshift lensing measurements are most sensitive. The combination of blue, green and red samples gives a value S-8 = 0.784 +/- 0.015, that is fully consistent with other low-redshift lensing measurements and in 2.4 sigma tension with the CMB predictions from Planck. This is noteworthy, because CMB lensing probes the same physics as previous galaxy lensing measurements, but with very different systematics, thus providing an excellent complement to previous measurements.

Automated summary

Recent lensing measurements at low redshifts suggest that the amplitude of lensing in the universe may be lower than predicted by the Lambda CDM model based on Planck CMB data. By analyzing the auto-and cross-correlation signal of unWISE galaxies and Planck CMB lensing maps, cosmological parameters at low redshifts have been inferred, showing tensions with the CMB predictions. The combination of blue, green, and red unWISE samples gives a value of S-8 = 0.784 +/- 0.015, consistent with other low-redshift lensing measurements and in tension with the CMB predictions from Planck.