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Biases to primordial non-Gaussianity measurements from CMB secondary anisotropies

Published version
Peer-reviewed

Repository DOI


Type

Article

Change log

Authors

Coulton, William 
Miranthis, Alexander 

Abstract

jats:titleABSTRACT</jats:title> jats:pOur view of the last-scattering surface in the cosmic microwave background (CMB) is obscured by secondary anisotropies, sourced by scattering, extragalactic emission, and gravitational processes between recombination and observation. Whilst it is established that non-Gaussianity from the correlation between the integrated-Sachs–Wolfe (ISW) effect and gravitational lensing can significantly bias primordial non-Gaussianity (PNG) searches, recent work by Hill suggests that other combinations of secondary anisotropies can also produce significant biases. Building on that work, we use the WebSky and Sehgal et al. simulations to perform an extensive examination of possible biases to PNG measurements for the local, equilateral and orthogonal shapes. For a Planck-like CMB experiment, without foreground cleaning, we find significant biases from cosmic infrared background (CIB)-lensing and thermal Sunyaev–Zel’dovich (tSZ)-lensing bispectra for the local and orthogonal templates, and from CIB and tSZ bispectra for the equilateral template. For future experiments, such as the Simons Observatory, biases from correlations between the ISW effect and the tSZ and CIB will also become important. Finally, we investigate the effectiveness of foreground-cleaning techniques to suppress these biases. We find that the majority of these biases are effectively suppressed by the internal-linear combination method with a total bias below the 1σ statistical error for both experiments. However, the small total bias arises from the cancellation of several 1σ biases for Planck-like experiments and 2σ biases for SO-like. As this cancellation is likely sensitive to the modelling, to ensure robustness against these biases, we recommend that explicit removal methods should be used.</jats:p>

Description

Keywords

cosmology: cosmic background radiation, cosmology: early Universe, theory

Journal Title

MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY

Conference Name

Journal ISSN

0035-8711
1365-2966

Volume Title

523

Publisher

Oxford University Press (OUP)

Rights

Publisher's own licence
Sponsorship
Science and Technology Facilities Council (ST/N000927/1)
Science and Technology Facilities Council (ST/S000623/1)
STFC (grant numbers ST/N000927/1 and ST/S000623/1)