Squeezed Limit non-Gaussianity Estimation with Cosmic Shear

TL;DR

This paper introduces a new, efficient method to estimate local primordial non-Gaussianity from galaxy lensing data, extending previous techniques to spherical coordinates and validating with simulations.

Contribution

The authors develop a simplified, computationally efficient approach to extract squeezed-limit non-Gaussianity information from large-scale lensing power spectra, compatible with multiple observables.

Findings

Validated the method with N-body simulations showing accurate $f_{NL}$ recovery.

Forecasted a $\sigma_{f_{NL}}$ of approximately 44 for LSST-like surveys.

Demonstrated the method's compatibility with other large-scale structure probes.

Abstract

We present a new method to constrain local primordial non-Gaussianity using the large-scale modulation of the local lensing power spectrum. Our work extends our recently proposed $\pi$-field method for primordial non-Gaussianity estimation to spherical coordinates and applies it to galaxy lensing. Our approach is computationally efficient and only requires binned multipole power spectra $C_\ell(z_1,z_2)$ on large scales, as well as their covariance. Our method is simpler to implement than a full bispectrum estimator, but still contains the full squeezed-limit information. We validate our model using a suite of N-body simulations and demonstrate its accuracy in recovering the $f_{\mathrm{NL}}$ values. We then perform a Fisher forecast for an LSST-like weak lensing survey, finding $\sigma_{f_{\mathrm{NL}}} \simeq 44$. Our approach readily combines with other $f_{\mathrm{NL}}$-sensitive fields such as kSZ velocity reconstruction and clustering-based $\pi$-fields, for a future combined $f_{\mathrm{NL}}$ estimator using various large-scale galaxy and CMB observables.