3,020 research outputs found
CMB low multipole alignments in the CDM and Dipolar models
The dipolar model \cite{Gordon:2005ai} has attracted much interest because it
may phenomenologically explain the CMB hemispherical power asymmetry found in
the WMAP and Planck data. Since such a model explicitly breaks isotropy at
large angular scales it is natural to wonder whether it can also explain other
CMB directional anomalies. Focusing on the low alignments and assuming
CDM, we confirm that the quadrupole/octupole and the
dipole/quadrupole/octupole alignments are anomalous with a significance up to
C.L., for both WMAP and Planck data. Moreover, we show for the first
time that such features are anomalous also in the dipolar model, roughly at the
same level as in CDM. We conclude that the dipolar model does not
provide a better fit to the data than the CDM.Comment: 13 pages, 2 figures and 4 table
Pre-Inflationary Relics in the CMB?
String Theory and Supergravity allow, in principle, to follow the transition
of the inflaton from pre-inflationary fast roll to slow roll. This introduces
an infrared depression in the primordial power spectrum that might have left an
imprint in the CMB anisotropy, if it occurred at accessible wavelengths. We
model the effect extending CDM with a scale related to the
infrared depression and explore the constraints allowed by {\sc Planck} data,
employing also more conservative, wider Galactic masks in the low resolution
CMB likelihood. In an extended mask with , we thus find \Delta =
(0.351 \pm 0.114) \times 10^{-3} \, \mbox{Mpc}^{-1}, at confidence
level, to be compared with a nearby value at with the standard
mask. With about 64 --folds of inflation, these values for
would translate into primordial energy scales GeV.Comment: 16 pages, 6 figures, 1 table. Final version to appear in Physics of
the Dark Universe. Contains: more detailed discussion of galactic masking,
improved estimat
Fast Spherical Harmonic Analysis: a quick algorithm for generating and/or inverting full sky, high resolution CMB Anisotropy maps
We present a fast algorithm for generating full sky, high resolution () simulations of the CMB anisotropy pattern. We also discuss the inverse
problem, that of evaluating from such a map the full set of 's and
the spectral coefficients . We show that using an Equidistant
Cylindrical Projection of the sky substantially speeds up the calculations.
Thus, generating and/or inverting a full sky, high resolution map can be easily
achieved with present day computer technology.Comment: 13 pages, LaTex, 5 PostScript figures included, 1 colour plate
available (PostScript version, 1.6 Mb) at http://itovf2.roma2.infn.it/natoli
The Evens and Odds of CMB Anomalies
The lack of power of large--angle CMB anisotropies is known to increase its
statistical significance at higher Galactic latitudes, where a string--inspired
pre--inflationary scale can also be detected. Considering the Planck
2015 data, and relying largely on a Bayesian approach, we show that the effect
is mostly driven by the \emph{even}-- harmonic multipoles with , which appear sizably suppressed in a way that is robust with
respect to Galactic masking, along with the corresponding detections of
. On the other hand, the first \emph{odd}-- multipoles are only
suppressed at high Galactic latitudes. We investigate this behavior in
different sky masks, constraining through even and odd multipoles, and
we elaborate on possible implications. We include low-- polarization data
which, despite being noise--limited, help in attaining confidence levels of
about 3 in the detection of . We also show by direct forecasts
that a future all--sky --mode cosmic--variance--limited polarization survey
may push the constraining power for beyond 5 .Comment: 49 pages, 19 figures. Figures and final discussion simplified,
references added. Final version to appear in Physics of the Dark Univers
Hemispherical power asymmetries in the WMAP 7-year low-resolution temperature and polarization maps
We test the hemispherical power asymmetry of the WMAP 7-year low-resolution
temperature and polarization maps. We consider two natural estimators for such
an asymmetry and exploit our implementation of an optimal angular power
spectrum estimator for all the six CMB spectra. By scanning the whole sky
through a sample of 24 directions, we search for asymmetries in the power
spectra of the two hemispheres, comparing the results with Monte Carlo
simulations drawn from the WMAP 7-year best-fit model. Our analysis extends
previous results to the polarization sector. The level of asymmetry on the ILC
temperature map is found to be compatible with previous results, whereas no
significant asymmetry on the polarized spectra is detected. Moreover, we show
that our results are only weakly affected by the a posteriori choice of the
maximum multipole considered for the analysis. We also forecast the capability
to detect dipole modulation by our methodology at Planck sensitivity.Comment: 7 pages, 9 figures. Accepted for publication in MNRA
CMB Polarization: Scientific Case and Data Analysis Issues
We review the science case for studying CMB polarization. We then discuss the
main issues related to the analysis of forth-coming polarized CMB data, such as
those expected from balloon-borne (e.g. BOOMERanG) and satellite (e.g. Planck)
experiments.Comment: 6 pages, 4 figures. To appear in "Astrophysical Polarized Background"
Workshop Proceedings, eds. S. Cecchini, S. Cortiglioni, R. Sault and C.
Sbarra, AIP, in pres
ROMA: a map-making algorithm for polarised CMB data sets
We present ROMA, a parallel code to produce joint optimal temperature and
polarisation maps out of multidetector CMB observations. ROMA is a fast,
accurate and robust implementation of the iterative generalised least squares
approach to map-making. We benchmark ROMA on realistic simulated data from the
last, polarisation sensitive, flight of BOOMERanG.Comment: Accepted for publication in Astronomy & Astrophysics. Version with
higher quality figures available at http://www.fisica.uniroma2.it/~cosmo/ROM
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