Anomalous variance in the WMAP data and Galactic Foreground residuals
  A previous work (Monteser\'in et al. 2008) estimated the CMB variance from
the three-year WMAP data, finding a lower value than expected from Gaussian
simulations using the WMAP best-fit cosmological model. We repeat the analysis
on the five-year WMAP data using a new estimator with lower bias and variance.
Our results confirm this anomaly at higher significance, namely with a p-value
of 0.31%. We perform the analysis using different exclusion masks, showing that
a particular region of the sky near the Galactic plane shows a higher variance
than 95.58% of the simulations whereas the rest of the sky has a lower variance
than 99.96% of the simulations. The relative difference in variance between
both regions is bigger than in 99.64% of the simulations. This anisotropic
distribution of power seems to be causing the anomaly since the model assumes
isotropy. Furthermore, this region has a clear frequency dependence between
41GHz and 61GHz or 94GHz suggesting that Galactic foreground residuals could be
responsible for the anomaly. Moreover, removing the quadrupole and the octopole
from data and simulations the anomaly disappears. The variance anomaly and the
previously reported quadrupole and octopole alignment seem therefore to be
related and could have a common origin. We discuss different possible causes
and Galactic foreground residuals seem to be the most likely one. These
residuals would affect the estimation of the angular power spectrum from the
WMAP data, which is used to generate Gaussian simulations, giving rise to an
inconsistency between the estimated and expected CMB variance. If the presence
of residuals is confirmed, the estimation of the cosmological parameters could
be affected.
