Journal Article

Gravitational lensing of the cosmic microwave background by non-linear structures

Philipp M. Merkel and Björn Malte Schäfer

in Monthly Notices of the Royal Astronomical Society

Published on behalf of The Royal Astronomical Society

Volume 411, issue 2, pages 1067-1076
Published in print February 2011 | ISSN: 0035-8711
Published online February 2011 | e-ISSN: 1365-2966 | DOI: http://dx.doi.org/10.1111/j.1365-2966.2010.17739.x
Gravitational lensing of the cosmic microwave background by non-linear structures

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Weak gravitational lensing changes the angular power spectra of the cosmic microwave background (CMB) temperature and polarization in a characteristic way containing valuable information for cosmological parameter estimation. So far, analytical expressions for the lensed CMB power spectra assume the probability density function (PDF) of the lensing excursion angle to be Gaussian. However, coherent light deflection by non-linear structures at low redshifts causes deviations from a pure Gaussian PDF. Working in the flat-sky limit, we develop a method for computing the lensed CMB power spectra which takes these non-Gaussian features into account. Our method does not assume any specific PDF but uses instead an expansion of the characteristic function of the lensing excursion angle into its moments. Measuring these in the CMB lensing deflection field obtained from the Millennium Simulation we show that the change in the lensed power spectra is only at the 0.1–0.4 per cent level on very small scales (Δθ≲ 4 arcmin, l≳ 2500) and demonstrate that the assumption of a Gaussian lensing excursion angle PDF is well applicable.

Keywords: gravitational lensing: weak; methods: analytical; methods: numerical; large-scale structure of Universe

Journal Article.  4277 words.  Illustrated.

Subjects: Astronomy and Astrophysics

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