Non-Gaussianity and CMB aberration and Doppler
  The peculiar motion of an observer with respect to the CMB rest frame induces
a deflection in the arrival direction of the observed photons (also known as
CMB aberration) and a Doppler shift in the measured photon frequencies. As a
consequence, aberration and Doppler effects induce non trivial correlations
between the harmonic coefficients of the observed CMB temperature maps. In this
paper we investigate whether these correlations generate a bias on
Non-Gaussianity estimators $f_{NL}$. We perform this analysis simulating a
large number of temperature maps with Planck-like resolution (lmax $= 2000$) as
different realizations of the same cosmological fiducial model (WMAP7yr). We
then add to these maps aberration and Doppler effects employing a modified
version of the HEALPix code. We finally evaluate a generalization of the
Komatsu, Spergel and Wandelt Non-Gaussianity estimator for all the simulated
maps, both when peculiar velocity effects have been considered and when these
phenomena have been neglected. Using the value $v/c=1.23 \times 10^{-3}$ for
our peculiar velocity, we found that the aberration/Doppler induced
Non-Gaussian signal is at most of about half of the cosmic variance $\sigma$
for $f_{NL}$ both in a full-sky and in a cut-sky experimental configuration,
for local, equilateral and orthogonal estimators. We conclude therefore that
when estimating $f_{NL}$ it is safe to ignore aberration and Doppler effects
{\it if} the primordial map is already Gaussian. More work is necessary however
to assess whether a map which contains Non-Gaussianity can be significantly
distorted by a peculiar velocity.
