Non-Gaussian deflections in iterative optimal CMB lensing reconstruction

Darwish, Omar, Belkner, Sebastian, Legrand, Louis, Carron, Julien and Fabbian, Giulio ORCID: https://orcid.org/0000-0002-3255-4695 2024. Non-Gaussian deflections in iterative optimal CMB lensing reconstruction. Physical Review D (particles, fields, gravitation, and cosmology) 110 (10) , 103520. 10.1103/physrevd.110.103520

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Abstract

The gravitational lensing signal from the cosmic microwave background (CMB) is highly valuable to constrain the growth of the structures in the Universe in a clean and robust manner over a wide range of redshifts. One of the theoretical systematics for lensing reconstruction is the impact of the lensing field non-Gaussianities on its estimators. Nonlinear matter clustering and post-Born lensing corrections are known to bias standard quadratic estimators to some extent, most significantly so in temperature. In this work, we explore the impact of non-Gaussian deflections on maximum a posteriori lensing estimators, which, in contrast to quadratic estimators, are able to provide optimal measurements of the lensing field. We show that these naturally reduce the induced non-Gaussian bias and lead to unbiased cosmological constraints in Λ cold dark matter at CMB-S4 noise levels without the need for explicit modeling. We also test the impact of assuming a non-Gaussian prior for the reconstruction; this mitigates the effect further slightly, but generally has little impact on the quality of the reconstruction. This shows that higher-order statistics of the lensing deflections are not expected to present a major challenge for optimal CMB lensing reconstruction in the foreseeable future.

Item Type:	Article
Date Type:	Published Online
Status:	Published
Schools:	Physics and Astronomy
Additional Information:	License information from Publisher: LICENSE 1: URL: https://link.aps.org/licenses/aps-default-license, Start Date: 2024-11-13
Publisher:	American Physical Society
ISSN:	2470-0010
Date of First Compliant Deposit:	9 December 2024
Date of Acceptance:	3 October 2024
Last Modified:	09 Dec 2024 10:30
URI:	https://orca.cardiff.ac.uk/id/eprint/174239

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