2008/03/28 by Asantha Cooray, Devdeep Sarkar, Paolo Serra +1
Earth and Planetary Sciences · Physics and Astronomy · #Cosmology and Gravitation Theories #Galaxies: Formation, Evolution, Phenomena #Geophysics and Gravity Measurements #astro-ph
paper · pdf · doi:10.1103/physrevd.77.123006
published as Phys.Rev.D77:123006,2008 · 9 Pages, 9 Figures, Submitted to PRD
arxiv created 2008/03/28 · openalex publication_date 2008/06/17 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/28
The bispectrum of cosmic microwave background (CMB) anisotropies is a well-known probe of the non-Gaussianity of primordial perturbations. Just as the intervening large-scale structure modifies the CMB angular power spectrum through weak gravitational lensing, the CMB primary bispectrum generated at the last scattering surface is also modified by lensing. We discuss the lensing modification to the CMB bispectrum and show that lensing leads to an overall decrease in the amplitude of the primary bispectrum at multipoles of interest between 100 and 2000 through additional smoothing introduced by lensing. Since weak lensing is not accounted for in current estimators of the primordial non-Gaussianity parameter, the existing measurements of fNL of the local model with WMAP out to lmax\ensuremath∼750 is biased low by about 6%. For a high resolution experiment such as Planck, the lensing modification to the bispectrum must be properly included when attempting to estimate the primordial non-Gaussianity or the bias will be at the level of 30%. For Planck, weak lensing increases the minimum detectable value for the non-Gaussianity parameter of the local type fNL to 7 from the previous estimate of about 5 without lensing. The minimum detectable value of fNL for a cosmic variance limited experiment is also increased from less than 3 to \ensuremath∼5.