An Estimate of the Primordial Non-Gaussianity Parameter f_NL Using the Needlet Bispectrum from WMAP

TL;DR

This paper estimates the primordial non-Gaussianity parameter f_NL using needlet bispectrum analysis of WMAP data, providing a statistically validated measurement with corrections for point source bias.

Contribution

It introduces a needlet bispectrum method for f_NL estimation and performs comprehensive consistency tests to validate the results against systematics.

Findings

Estimated f_NL=84 +/- 40 after bias correction

Results are consistent across different frequency channels and masks

Method effectively detects primordial non-Gaussianity in CMB data

Abstract

We use the full bispectrum of spherical needlets applied to the WMAP data of the cosmic microwave background as an estimator for the primordial non-Gaussianity parameter f_NL. We use needlet scales up to l_max=1000 and the KQ75 galactic cut and find f_NL=84 +/- 40 corrected for point source bias. We also introduce a set of consistency tests to validate our results against the possible influence of foreground residuals or systematic errors. In particular, fluctuations in the value of f_NL obtained from different frequency channels, different masks and different multipoles are tested against simulated maps. All variations in f_NL estimates are found statistically consistent with simulations.