Prospects for detecting dipolar asymmetry in Planck polarization data

Abstract

In the 2015 Planck Isotropy and Statistics article, the dipolar asymmetry previously found in the WMAP data (Hansen et al. 2009) was found to extend to the smallest scales. While the statistical significance of this anomaly is highly debated, with the coming release of the high resolution Planck polarization data, it will finally be possible to perform the same tests on the $E$-mode polarization. Here, the prospects of detecting a similar asymmetry in the $E$-mode polarization data is investigated, when the higher noise level of the polarization data is taken into account. A set of non-isotropic temperature simulations is made by rotating multipole maps in order to mimic the clustering present in the Planck data. By rotating the multipoles in blocks of $10l$ for $l\leq 200$ and $50l$ for $l>200$, results similar to what is seen in the Planck data is produced. By extending the analysis to polarization, it is shown that when rotating the $E$-modes similarly to the best-fit temperature rotation parameters, similar clustering and significance is achieved in the noiseless scenario. Adding noise of similar amplitude as what one would expect from the Planck polarization data causes the significance to vanish.