Alessio Notari, Miguel Quartin, Riccardo Catena
Our peculiar motion with respect to the CMB rest frame represents a preferred direction in the observed CMB sky since it induces an apparent deflection of the observed CMB photons (aberration) and a shift in their frequency (Doppler). Both effects distort the multipoles a_{ell m}'s at all ell's. Such effects are real as it has been recently measured for the first time by Planck according to what was proposed in recent papers. However, the common lore when estimating a power spectrum from CMB is to consider that Doppler affects only the ell=1 multipole, neglecting any other corrections. In this letter we use simulations of the CMB sky in a boosted frame with a peculiar velocity \beta = v/c = 0.00123 in order to assess the impact of such effect on power spectrum estimations in different regions of the sky. We show that the boost induces a north-south asymmetry in the power spectrum which is highly significant and non-negligible, of about (0.75 \pm 0.15)% for half-sky cuts when going up to ell = 2500. We suggest that these effects are relevant and may account for some of the north-south asymmetries seen in the Planck data, being especially important at small scales.
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http://arxiv.org/abs/1304.3506
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