The lack of power at large angular scales in the CMB temperature anisotropy pattern is a feature known to depend on the size of the Galactic mask. Not only the large scale anisotropy power in the CMB is lower than the best-fit Lambda CDM model predicts, but most of the power seems to be localised close to the Galactic plane, making high-Galactic latitude regions more anomalous. We assess how likely the latter behaviour is in a Lambda CDM model by extracting simulations from the Planck 2018 fiducial model. By comparing the former to Planck data in different Galactic masks, we reproduce the anomaly found in previous works, at a statistical significance of similar to 3 sigma. This result suggests the existence of a bizzarre correlation between the particular orientation of the Galaxy and the lack of power anomaly. To test this hypothesis, we perform random rotations of the Planck 2018 data and compare these to similarly rotated Lambda CDM realisations. We find that, among all possible rotations, the lower-tail probability of the observed high-Galactic latitude data variance is still low at the level of 2.8 sigma. Furthermore, the lowering trend of the variance when moving from low- to high-Galactic latitude is anomalous in the data at similar to 3 sigma when comparing to Lambda CDM rotated realisations. This shows that the lack of power at high Galactic latitude is substantially stable against the "look elsewhere" effect induced by random rotations of the Galaxy orientation. Moreover, this analysis turns out to be substantially stable if we employ, in place of generic Lambda CDM simulations, a specific set whose variance is constrained to reproduce the observed data variance.

Is the lack of power anomaly in the CMB correlated with the orientation of the Galactic plane?

Natale, U.
Primo
;
Gruppuso, A.
Secondo
;
Molinari, D.
Penultimo
;
Natoli, P.
Ultimo
2019

Abstract

The lack of power at large angular scales in the CMB temperature anisotropy pattern is a feature known to depend on the size of the Galactic mask. Not only the large scale anisotropy power in the CMB is lower than the best-fit Lambda CDM model predicts, but most of the power seems to be localised close to the Galactic plane, making high-Galactic latitude regions more anomalous. We assess how likely the latter behaviour is in a Lambda CDM model by extracting simulations from the Planck 2018 fiducial model. By comparing the former to Planck data in different Galactic masks, we reproduce the anomaly found in previous works, at a statistical significance of similar to 3 sigma. This result suggests the existence of a bizzarre correlation between the particular orientation of the Galaxy and the lack of power anomaly. To test this hypothesis, we perform random rotations of the Planck 2018 data and compare these to similarly rotated Lambda CDM realisations. We find that, among all possible rotations, the lower-tail probability of the observed high-Galactic latitude data variance is still low at the level of 2.8 sigma. Furthermore, the lowering trend of the variance when moving from low- to high-Galactic latitude is anomalous in the data at similar to 3 sigma when comparing to Lambda CDM rotated realisations. This shows that the lack of power at high Galactic latitude is substantially stable against the "look elsewhere" effect induced by random rotations of the Galaxy orientation. Moreover, this analysis turns out to be substantially stable if we employ, in place of generic Lambda CDM simulations, a specific set whose variance is constrained to reproduce the observed data variance.
Natale, U.; Gruppuso, A.; Molinari, D.; Natoli, P.
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11392/2417160
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