Improving CMB non-Gaussianity estimators using tracers of local structure

Mead, James M G, Lewis, Antony and King, Lindsay (2011) Improving CMB non-Gaussianity estimators using tracers of local structure. Physical Review D, 83 (2). 023507. ISSN 1550-7998

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Local non-Gaussianity causes correlations between large-scale perturbation modes and the small-scale power. The large-scale CMB signal has contributions from the integrated Sachs-Wolfe (ISW) effect, which does not correlate with the small-scale power. If this ISW contribution can be removed, the sensitivity to local non-Gaussianity is improved. Gravitational lensing and galaxy counts can be used to trace the ISW contribution; in particular, we show that the CMB lensing potential is highly correlated with the ISW signal. We construct a nearly optimal estimator for the local non-Gaussianity parameter fNL and investigate to what extent we can use this to decrease the variance on fNL. We show that the variance can be decreased by up to 20% at Planck sensitivity using galaxy counts. CMB lensing is a good bias-independent ISW tracer for future more sensitive observations, though the fractional decrease in variance is small if good polarization data are also available.

Item Type: Article
Schools and Departments: School of Mathematical and Physical Sciences > Physics and Astronomy
Subjects: Q Science > QB Astronomy
Q Science > QC Physics
Depositing User: Antony Lewis
Date Deposited: 06 Feb 2012 20:01
Last Modified: 02 Jul 2019 20:47

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