Non-gaussianity in the foreground-reduced CMB maps
  [Abridged]: A detection or nondetection of primordial non-Gaussianity by
using the CMB data is crucial not only to discriminate inflationary models but
also to test alternative scenarios. Non-Gaussianity offers, therefore, a
powerful probe of the physics of the primordial universe. The extraction of
primordial non-Gaussianity is a difficult enterprise since several effects of
non-primordial nature can produce non-Gaussianity. Most of the Gaussianity
analyses of CMB data have been performed by using part-sky frequency, where
masks are used to deal with the galactic diffuse foreground emission. However,
full-sky map seems to be potentially more appropriate to test for Gaussianity
of the CMB data. On the other hand, masks can induce bias in some
non-Gaussianity analyses. Here we use two recent large-angle non-Gaussianity
indicators, based on skewness and kurtosis of large-angle patches of CMB maps,
to examine the question of non-Gaussianity in the available full-sky five-year
and seven-year WMAP maps. We show that these full-sky foreground-reduced maps
present a significant deviation from Gaussianity of different levels, which
vary with the foreground-reducing procedures. We also make a Gaussianity
analysis of the foreground-reduced five-year and seven-year WMAP maps with a
KQ75 mask, and compare with the similar analysis performed with the full-sky
foreground-reduced maps. This comparison shows a significant reduction in the
levels of non-Gaussianity when the mask is employed, which provides indications
on the suitability of the foreground-reduced maps as Gaussian reconstructions
of the full-sky CMB.
