116 research outputs found
Mapping possible non-Gaussianity in the Planck maps
[Abridged.] It is conceivable that no single statistical estimator can be
sensitive to all forms and levels of non-Gaussianity that may be present in
observed CMB data. In recent works a statistical procedure based upon the
calculation of the skewness and kurtosis of the patches of CMB sky-sphere has
been proposed and used to find out significant large-angle deviation from
Gaussianity in the foreground-reduced WMAP maps. Here we address the question
as to how the analysis of Gaussianity of WMAP maps is modified if the
foreground-cleaned Planck maps are used, therefore extending and complementing
the previous analyses in several regards. We carry out a new analysis of
Gaussianity with the available nearly full-sky foreground-cleaned Planck maps.
As the foregrounds are cleaned through different component separation
procedures, each of the resulting Planck maps is then tested for Gaussianity.
We determine quantitatively the effects for Gaussianity of masking the
foreground-cleaned Planck maps with the INPMASK, VALMASK, and U73 Planck masks.
We show that although the foreground-cleaned Planck maps present significant
deviation from Gaussianity of different degrees when the less severe INPMASK
and VALMASK are used, they become consistent with Gaussianity as detected by
our indicator when masked with the union U73 mask. A slightly smaller
consistency with Gaussianity is found when the indicator is employed, which
seems to be associated with large-angle anomalies reported by the Planck team.
Finally, we examine the robustness of the Gaussianity analyses with respect to
the noise pixel's as given by the Planck team, and show that no appreciable
changes arise when is incorporated into the maps. The results of our analyses
provide important information about the suitability of the foreground-cleaned
Planck maps as Gaussian reconstructions of the CMB sky.Comment: 10 pages, 4 figures. V2: Version to appear in A&A (2014),
reformatted, typos corrected, references added, a word added in the titl
A note on the large-angle anisotropies in the WMAP cut-sky maps
Recent analyses of the WMAP data seem to indicate the possible presence of
large-angle anisotropy in the Universe. If confirmed, these can have important
consequences for our understanding of the Universe. A number of attempts have
recently been made to establish the reality and nature of such anisotropies in
the CMB data. Among these is a directional indicator recently proposed by the
authors. A distinctive feature of this indicator is that it can be used to
generate a sky map of the large-scale anisotropies of the CMB maps. Applying
this indicator to full-sky temperature maps we found a statistically
significant preferred direction. The full-sky maps used in these analyses are
known to have residual foreground contamination as well as complicated noise
properties. Thus, here we performed the same analysis for a map where regions
with high foreground contamination were removed. We find that the main feature
of the full-sky analysis, namely the presence of a significant axis of
asymmetry, is robust with respect to this masking procedure. Other subtler
anomalies of the full-sky are on the other hand no longer present.Comment: 10 pages, 3 figeres. We performed a similar analysis of
arXiv:astro-ph/0511666 by considering the LILC map with a Kp2 sky cut, and
find that the presence of a significant axis of asymmetry is robust with
respect to this masking procedur
A method to search for topological signatures in the angular distribution of cosmic objects
We present a method to search for large angular-scale correlations, termed
topological signatures, in the angular distribution of cosmic objects, which
does not depend on cosmological models or parameters and is based only on the
angular coordinates of the objects. In order to explore Cosmic Microwave
Background temperature fluctuations data, we applied this method to simulated
distributions of objects in thin spherical shells located in three different
multiply-connected Euclidean 3-spaces (, , and ), and found
that the topological signatures due to these topologies can be revealed even if
their intensities are small. We show how to detect such signatures for the
cases of full-sky and partial-sky distributions of objects. This method can
also be applied to other ensembles of cosmic objects, like galaxies or quasars,
in order to reveal possible angular-scale correlations in their distributions.Comment: 11 pages, 18 figures. To appear in A&
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