2023/10/19 by Goldstein, Samuel, Philcox, Oliver H. E., Hill, J. Colin +2 · 1 citation
#Cosmology and Nongalactic Astrophysics (astro-ph.CO) #FOS: Physical sciences #General Relativity and Quantum Cosmology (gr-qc)
paper · doi:10.48550/arxiv.2310.12959
We introduce a non-perturbative method to constrain the amplitude of local-type primordial non-Gaussianity (f\rm NL) using squeezed configurations of the CMB lensing convergence and cosmic shear bispectra. First, we use cosmological consistency relations to derive a model for the squeezed limit of angular auto- and cross-bispectra of lensing convergence fields in the presence of f\rm NL. Using this model, we perform a Fisher forecast with specifications expected for upcoming CMB lensing measurements from the Simons Observatory and CMB-S4, as well as cosmic shear measurements from a Rubin LSST/Euclid-like experiment. Assuming a minimum multipole ℓ\rm min=10 and maximum multipole ℓ\rm max=1400, we forecast σ_f\rm NL=175 (95) for Simons Observatory (CMB-S4). Our forecasts improve considerably for an LSST/Euclid-like cosmic shear experiment with three tomographic bins and ℓ\rm min=10 and ℓ\rm max=1400 (5000) with σ_f\rm NL=31 (16). A joint analysis of CMB-S4 lensing and LSST/Euclid-like shear yields little gain over the shear-only forecasts; however, we show that a joint analysis could be useful if the CMB lensing convergence can be reliably reconstructed at larger angular scales than the shear field. The method presented in this work is a novel and robust technique to constrain local primordial non-Gaussianity from upcoming large-scale structure surveys that is completely independent of the galaxy field (and therefore any nuisance parameters such as bϕ), thus complementing existing techniques to constrain f\rm NL using the scale-dependent halo bias.