CMB statistical isotropy confirmation at all scales using multipole vectors

Abstract

We present an efficient numerical code and conduct, for the first time, a 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 avoid a posteriori choices and use pre-defined ranges of scales $\ell \in [2,30]$, $\ell \in [2,600]$ and $\ell \in [2,1500]$ in our analyses. We find that all four masked Planck maps, from both 2015 and 2018 releases, are in agreement with statistical isotropy for $\ell \in [2,30]$, $\ell \in [2,600]$. For $\ell \in [2,1500]$ we detect anisotropies but this is indicative of simply the anisotropy in the noise: there is no anisotropy for $\ell <1300$ and an increasing level of anisotropy at higher multipoles. Our findings of no large-scale anisotropies seem to be a consequence of avoiding \emph{a posteriori} statistics. We also find that the degree of anisotropy in the full sky (i.e. unmasked) maps vary enormously (between less than 5 and over 1000 standard deviations) among the different mapmaking procedures and data releases.

v5: [erratum] replaced Figure 6 which in v4 was depicting the masked maps instead of the unmasked ones

References in corpus (2)

• Planck CMB Anomalies: Astrophysical and Cosmological Secondary Effects and the Curse of Masking
• On the proper kinetic quadrupole CMB removal and the quadrupole anomalies

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