568 research outputs found
The CMB Derivatives of Planck's Beam Asymmetry
We investigate the anisotropy in cosmic microwave background Planck maps due
to the coupling between its beam asymmetry and uneven scanning strategy.
Introducing a pixel space estimator based on the temperature gradients, we find
a highly significant (~20 \sigma) preference for these to point along ecliptic
latitudes. We examine the scale dependence, morphology and foreground
sensitivity of this anisotropy, as well as the capability of detailed Planck
simulations to reproduce the effect, which is crucial for its removal, as we
demonstrate in a search for the weak lensing signature of cosmic defects.Comment: 5 pages, 9 figures Published in MNRA
A close examination of cosmic microwave background mirror-parity after Planck
Previous claims of significant evidence for mirror-parity in the large-scale
cosmic microwave background (CMB) data from the Wilkinson Microwave Anisotropy
Probe (WMAP) experiment have been recently echoed in the first study of
isotropy and statistics of CMB data from Planck. We revisit these claims with a
careful analysis of the latest data available. We construct statistical
estimators in both harmonic and pixel space, test them on simulated data with
and without mirror-parity symmetry, apply different Galactic masks, and study
the dependence of the results on arbitrary choices of free parameters. We
confirm that the data exhibit evidence for odd mirror-parity at a significance
which reaches as high as ~ 99 per cent C.L., under some circumstances. However,
given the inherent biases in the pixel-based statistic and the dependence of
both pixel and harmonic space statistics on the particular form of Galactic
masking and other a-posteriori choices, we conclude that these results are not
in significant tension with the predictions of the concordance cosmological
model.Comment: 9 pages, 5 figures, minor changes, as published in MNRA
Parity in the CMB: Space Oddity
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 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 CDM simulations. Focusing on low multipoles, with 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 effect.Comment: 6 pages, 7 figures. Accepted for publication in The Astrophysical
Journa
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