Kavli Affiliate: Anthony Challinor
| First 5 Authors: William Coulton, Alexander Miranthis, Anthony Challinor, ,
| Summary:
Our 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 (2018) has suggested that other combinations of secondary anisotropies can
also produce significant biases. Building on that work, we use the WebSky and
Sehgal et al.(2010) 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 whether foreground-cleaning techniques are able to suppress
these biases sufficiently. We find that the majority of these biases are
effectively suppressed by the internal-linear-combination method and the total
bias to Planck-like and SO-like experiments is less than the $1,sigma$
statistical error. However, the small total bias arises from the cancellation
of several $1,sigma$ biases for Planck-like experiments and $2,sigma$
biases for SO-like. As this cancellation is likely sensitive to the precise
modelling, to ensure robustness against these biases explicit removal methods
should be used, likely at the cost of decreased constraining power.
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