Detecting deviations from Gaussianity in high-redshift CMB lensing maps

While the probability density function of the cosmic microwave background (CMB) convergence field approximately follows a Gaussian distribution, primordial non-Gaussianities, and small contributions from structures at low redshifts make the overall distribution slightly non-Gaussian. Some of the late-time component can be modelled using the distribution of galaxies and subtracted off from the original CMB lensing map to produce a map of matter distribution at high redshifts. Using this high-redshift mass map, we are able to directly study the early phases of structure formation. In this work, we forecast the detectability of signatures of non-Gaussianity due to non-linear structure formation at z > 1.2. Assuming the optimal case of no systematics, we find that it is challenging to detect such signatures in current surveys, but future experiments such as the deep field of CMB-S4 will be able to make detections of & SIM;7 & sigma;.

Automated summary

This study examines the probability density function of the cosmic microwave background (CMB) convergence field and finds that the overall distribution is slightly non-Gaussian due to primordial non-Gaussianities and contributions from structures at low redshifts. By modelling the distribution of galaxies and subtracting the late-time component from the original CMB lensing map, a high-redshift mass map is obtained, allowing for the direct study of early phases of structure formation. The detectability of non-Gaussianity signatures from non-linear structure formation at z > 1.2 is forecasted in this work, and it is found that current surveys may face challenges in detecting such signatures, while future experiments like the deep field of CMB-S4 will have the capability to make detections at & SIM;7 & sigma;.