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 Cℓ, our results are independent from the assumed cosmological model. We avoid a posteriori choices and use a pre-defined range of scales ℓ ∈ [ 2 , 30 ] , ℓ ∈ [ 2 , 600 ] and ℓ ∈ [ 2 , 1500 ] in our analyses. We find that all four masked Planck maps, both from the 2015 and 2018 releases, are in agreement with statistical isotropy for ℓ ∈ [ 2 , 30 ] , ℓ ∈ [ 2 , 600 ]. For ℓ ∈ [ 2 , 1500 ] we detect anisotropies but this is indicative of simply the anisotropy in the noise: there is no anisotropy for ℓ < 1300 and an increasing level of anisotropy at higher multipoles. Our finding of no large-scale anisotropies seem to be a consequence of avoiding 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.
- Publication:
-
Physics of the Dark Universe
- Pub Date:
- December 2020
- DOI:
- 10.1016/j.dark.2020.100608
- arXiv:
- arXiv:1812.02654
- Bibcode:
- 2020PDU....3000608O
- Keywords:
-
- Observational cosmology;
- Cosmic microwave background;
- Statistical isotropy;
- Multipole vectors;
- Astrophysics - Cosmology and Nongalactic Astrophysics;
- Astrophysics - Instrumentation and Methods for Astrophysics;
- General Relativity and Quantum Cosmology
- E-Print:
- v5: [erratum] replaced Figure 6 which in v4 was depicting the masked maps instead of the unmasked ones