Effect of lensing non-Gaussianity on the CMB power spectra

Lewis, Antony and Pratten, Geraint (2016) Effect of lensing non-Gaussianity on the CMB power spectra. Journal of Cosmology and Astroparticle Physics, 2016 (12). 003. ISSN 1475-7516

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Observed CMB anisotropies are lensed, and the lensed power spectra can be calculated accurately assuming the lensing deflections are Gaussian. However, the lensing deflections are actually slightly non-Gaussian due to both non-linear large-scale structure growth and post-Born corrections. We calculate the leading correction to the lensed CMB power spectra from the non-Gaussianity, which is determined by the lensing bispectrum. The lowest-order result gives ∼0.3% corrections to the BB and EE polarization spectra on small-scales, however we show that the effect on EE is reduced by about a factor of two by higher-order Gaussian lensing smoothing, rendering the total effect safely negligible for the foreseeable future. We give a simple analytic model for the signal expected from skewness of the large-scale lensing field; the effect is similar to a net demagnification and hence a small change in acoustic scale (and therefore out of phase with the dominant lensing smoothing that predominantly affects the peaks and troughs of the power spectrum).

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Research Centres and Groups: Astronomy Centre
Subjects: Q Science > QB Astronomy
Depositing User: Richard Chambers
Date Deposited: 13 Jan 2017 15:02
Last Modified: 06 Dec 2017 02:00
URI: http://srodev.sussex.ac.uk/id/eprint/66172

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Project NameSussex Project NumberFunderFunder Ref
Precision cosmological parameters : CosmoParsG1365EUROPEAN UNION616170 ERC-2013-CoG
Astrophysics and Cosmology - Sussex Consolidated GrantG1291STFC-SCIENCE AND TECHNOLOGY FACILITIES COUNCILST/L000652/1