Detection of primordial non-Gaussianity (fNL) in the WMAP 3-year data at above 99.5% confidence

TL;DR

This paper reports a significant detection of primordial non-Gaussianity in the WMAP 3-year CMB data, challenging standard inflation models and providing new insights into early universe physics.

Contribution

It presents the first robust detection of local-type primordial non-Gaussianity using the full WMAP 3-year data with a bispectrum estimator, avoiding arbitrary scale cuts.

Findings

fNL measured between 27 and 147 at 95% confidence

Detection significance exceeds 99.5% confidence level

Results are robust against analysis variations and systematic checks

Abstract

We present evidence for the detection of primordial non-Gaussianity of the local type (fNL), using the temperature information of the Cosmic Microwave Background (CMB) from the WMAP 3-year data. We employ the bispectrum estimator of non-Gaussianity described in (Yadav et al. 2007) which allows us to analyze the entirety of the WMAP data without an arbitrary cut-off in angular scale. Using the combined information from WMAP's two main science channels up to lmax=750 and the conservative Kp0 foreground mask we find 27 < fNL < 147 at 95% C.L., with a central value of fNL=87. This corresponds to a rejection of fNL=0 at more than 99.5% significance. We find that this detection is robust to variations in lmax, frequency and masks, and that no known foreground, instrument systematic, or secondary anisotropy explains our signal while passing our suite of tests. We explore the impact of several analysis choices on the stated significance and find 2.5 sigma for the most conservative view. We conclude that the WMAP 3-year data disfavors canonical single field slow-roll inflation.