http://arxiv.org/abs/1812.02654
We present the first null and model-independent CMB test of statistical isotropy using Multipole Vectors (MVs) at all scales. Because MVs are insensitive to the angular power spectrum $C_\ell$, our results are independent from the assumed cosmological model. We test all Planck temperature maps in the range $\ell \in [2,1500]$, where the (anisotropic) instrumental noise can safely be neglected. All four masked Planck maps, both from the 2015 and 2018 releases, are shown to be in agreement with statistical isotropy. Even some of the full sky (i.e., unmasked) maps are consistent with isotropy, to wit: NILC 2015 and 2018, SMICA 2015 and 2018, and Commander 2015. On the other hand, both unmasked SEVEM 2015 and 2018 are ruled out as statistically isotropic at >~ 80 sigma; in the unmasked Commander 2018 the anisotropy is blatant (~6000 sigma), probably due to the simplified foreground model employed in this release. This shows that MVs can be a useful tool in the detection of residual foreground contamination in CMB maps and thus in determining which regions to mask.
R. Oliveira, T. Pereira and M. Quartin
Fri, 7 Dec 18
20/66
Comments: 6 pages, 5 figures, 3 tables. Comments are welcome
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