Primordial Non-Gaussianity (fNL) in WMAP data

We present evidence for the detection of primordial non- Gaussianity of the local type ($f_{NL}$), 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 $\ell_{max}=750$ and the conservative Kp0 foreground mask we find $26.9 < \mathbf {f_ {\rm NL}} < 146.7$ at $95 \%$ C.L., with a central value of $f_ {NL}=86.8$. This corresponds to a rejection of $f_{NL}=0$ at more than 99.5\% significance. We find that this detection is robust to variations in $l_{max}$, frequency and masks. We conclude that the WMAP 3-year data disfavors single field slow- roll inflation.