Parity in the CMB: Space Oddity

Abstract

We search for a direction in the sky that exhibits parity symmetry under reflections through a plane. We use the natural estimator, which compares the power in even and odd $\ell +m$ multipoles, and apply minimal blind masking of outliers to the ILC map in order to avoid large errors in the reconstruction of multipoles. The multipoles of the cut sky are calculated both naively and by using the covariance inversion method and we estimate the significance of our results using $\Lambda$CDM simulations. Focusing on low multipoles, $2\le \ell \le {\ell }_{\max }$ with ${\ell }_{\max }=5,6$ or even 7, we find two perpendicular directions of even and odd parity in the map. While the even parity direction does not appear significant, the odd direction is quite significant -- at least a $3.6\sigma$ effect.

6 pages, 7 figures. Accepted for publication in The Astrophysical Journal

References in corpus (5)

• CMB multipole measurements in the presence of foregrounds
• Cosmic Bubble Collisions
• Giant Rings in the CMB Sky
• Avoiding bias in reconstructing the largest observable scales from partial-sky data
• Symmetry of the CMB sky as a new test of its statistical isotropy. Non Cosmological Octupole?

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