Preprint typeset using L ATEX style emulateapj v. 10/09/06 DIRECTIONAL VARIATIONS OF THE NON-GAUSSIANITY PARAMETER fNL

• Main Authors: Øystein Rudjord, Frode K. Hansen, Xiaohong Lan, Michele Liguori, Domenico Marinucci, Sabino Matarrese
• Other Authors: The Pennsylvania State University CiteSeerX Archives
• Format: Text
• Language: English
• Published: 2009
• Subjects: South Pole; South pole
• Online Access: http://citeseerx.ist.psu.edu/viewdoc/summary?doi=10.1.1.250.880; http://arxiv.org/pdf/0906.3232v1.pdf

We investigate local variations of the primordial non-Gaussianity parameter fNL in the WMAP data, looking for possible influence of foreground contamination in the full-sky estimate of fNL. We first improve the needlet bispectrum estimate in ( Rudjord et al. 2009) on the full-sky to fNL = 73±31 using the KQ75 mask on the co-added V+W channel. We find no particular values of fNL estimates close to the galactic plane and conclude that foregrounds are unlikely to affect the estimate of fNL in the V and W bands even for the smaller KQ85 mask. In the Q band however, we find unexpectedly high values of fNL in local estimates close to the galactic mask, as well as significant discrepancies between Q band estimates and V/W band estimates. We therefore conclude that the Q band is too contaminated to be used for non-Gaussianity studies even with the larger KQ75 mask. We further noted that the local fNL estimates on the V+W channel are positive on all equatorial bands from the north to the south pole. The probability for this to happen in a universe with fNL = 0 is less than one percent.