437 research outputs found
Ionization history of the cosmic plasma in the light of the recent CBI and future PLANCK data
The paper is devoted to the methods of determination of the cosmological
parameters from recent CMB observations. We show that the more complex models
of kinetics of recombination with a few "missing" parameters describing the
recombination process provide better agreement between measured and expected
characteristics of the CMB anisotropy. In particular, we consider the external
sources of the Ly-{alpha} and Ly-{c} radiation and the model with the strong
clustering of baryonic component. These factors can constrain the estimates of
the cosmological parameters usually discussed. We demonstrate also that the
measurements of polarization can improve these estimates and, for the precision
expected for the PLANCK mission, allow to discriminate a wide class of models.Comment: 25 pages, 7 figures, extended and corrected after the referee report.
Accepted in Ap
Is the CMB asymmetry due to the kinematic dipole?
Parity violation found in the Cosmic Microwave Background (CMB) radiation is
a crucial clue for the non-standard cosmological model or the possible
contamination of various foreground residuals and/or calibration of the CMB
data sets. In this paper, we study the directional properties of the CMB parity
asymmetry by excluding the modes in the definition of parity parameters.
We find that the preferred directions of the parity parameters coincide with
the CMB kinematic dipole, which implies that the CMB parity asymmetry may be
connected with the possible contamination of the residual dipole component. We
also find that such tendency is not only localized at , but in the
extended multipole ranges up to .Comment: 17 pages, 5 figures, 2 tables, improved version, ApJ accepte
Phase analysis of the cosmic microwave background from an incomplete sky coverage
Phases of the spherical harmonic analysis of full-sky cosmic microwave
background (CMB) temperature data contain useful information complementary to
the ubiquitous angular power spectrum. In this letter we present a new method
of phase analysis on incomplete sky maps. It is based on Fourier phases of
equal-latitude pixel rings of the map, which are related to the mean angle of
the trigonometric moments from the full-sky phases. They have an advantage for
probing regions of interest without tapping polluted Galactic plane area, and
can localize non-Gaussian features and departure from statistical isotropy in
the CMB.Comment: 5 pages, 3 figures submitted to MNRAS Letters, replaced with minor
change
The Cosmological Gene Project: cluster analysis of the atmospheric fluctuations on arcmin-scale imaging of the Cosmic Microwave Background
We discuss some aspects of the Cosmological Gene Project started at the
Special Astrophysical Observatory (Russia) in 1999. The goal of the project is
to measure the anisotropy and polarization of the Cosmic Microwave Background
(CMB) and investigation of atmospheric fluctuations and foreground on
arcmin-scales using the radio-telescope RATAN-600. We develop the cluster
analysis of one-dimensional random fields for the application to the RATAN-600
scans. We analyze the specific properties of peak clusterisation in the
RATAN-600 scans which to separate the primordial CMB signal from noise.Comment: Submitted to Astronomy & Astrophysic
Auto and cross correlation of phases of the whole-sky CMB and foreground maps from the 1-year WMAP data
The issue of non-Gaussianity is not only related to distinguishing the
theories of the origin of primordial fluctuations, but also crucial for the
determination of cosmological parameters in the framework of inflation
paradigm. We present an advenced method for testing non-Gaussianity on the
whole-sky CMB anisotropies. This method is based on the Kuiper's statistic to
probe the two-dimensional uniformity on a periodic mapping square associating
phases: return mapping of phases of the derived CMB (similar to auto
correlation) and cross correlations between phases of the derived CMB and
foregrounds. Since phases reflect morphology, detection of cross correlation of
phases signifies the contamination of foreground signals in the derived CMB
map. The advantage of this method is that one can cross check the auto and
cross correlation of phases of the derived CMB and foregrounds, and mark off
those multipoles in which the non-Gaussianity results from the foreground
contaminations. We apply this statistic on the derived signals from the 1-year
WMAP data. The auto-correlations of phases from the ILC map shows the
significance above 95% CL against the random phase hypothesis on 17 spherical
harmonic multipoles, among which some have pronounced cross correlations with
the foreground maps. We conclude that most of the non-Gaussianity found in the
derived CMB maps are from foreground contaminations, except, among others, l=6.
With this method we are better equipped to approach the issue of
non-Gaussianity of primordial origin for the upcoming PLANCK mission.Comment: 2 figures added: new representation of reconstructed (from 1D Fourier
composition) DT distribution for each multipole number el
Symmetry of the CMB sky as a new test of its statistical isotropy. Non Cosmological Octupole?
In this article we propose a novel test for statistical anisotropy of the
CMB. The test is based on the fact, that the Galactic foregrounds have a
remarcably strong symmetry with respect to their antipodal points and with
respect to the Galactic plane, while the cosmological signal should not be
symmetric or asymmetric under these transitions. We have applied the test for
the octupole component of the WMAP ILC 7 map, by looking at a_3,1 and a_3,3,
and their ratio to a_3,2 both for real and imaginary values. We find abnormal
symmetry of the octupole component at the level of 0.58%, compared to Monte
Carlo simulations. By using the analysis of the phases of the octupole we found
remarkably strong cross-correlations between the phases of kinematic dipole and
ILC 7 octupole, in full agreement with previous results. We further test the
multipole range 2<l<100, by investigating the ratio between the l+m=even and
l+m=odd parts of power spectra. We compare the results to simulations of a
Gaussian random sky, and find significant departure from the statistically
isotropic and homogeneous case, for a very broad range of multipoles. We found
that for the most prominent peaks of our estimator, the phases of the
corresponding harmonics are coherent with phases of the octupole. We believe,
our test would be very useful for detections of various types of residuals of
the foreground and systematic effects at very a broad range of multipoles 2 < l
< 1500-3000 for the forthcoming PLANCK CMB map, before any conclusions about
primordial non-Gaussianity and statistical anisotropy of the CMB.Comment: Slight modifications, based on proofread version from JCAP. 17 pages,
9 figures, 3 table
General Statistical properties of the CMB Polarization field
The distribution of the polarization of the Cosmic Microwave Background (CMB)
in the sky is determined by the hypothesis of random Gaussian distribution of
the primordial density perturbations. This hypotheses is well motivated by the
inflationary cosmology. Therefore, the test of consistency of the statistical
properties of the CMB polarization field with the Gaussianity of primordial
density fluctuations is a realistic way to study the nature of primordial
inhomogeneities in the Universe. This paper contains the theoretical
predictions of the general statistical properties of the CMB polarization
field. All results obtained under assumption of the Gaussian nature of the
signal. We pay the special attention to the following two problems. First, the
classification and statistics of the singular points of the polarization field
where polarization is equal to zero. Second, the topology of contours of the
value of the degree of polarization. We have investigated the percolation
properties for the zones of ``strong'' and ``weak'' polarization. We also have
calculated Minkowski functionals for the CMB polarization field. All results
are analytical.Comment: Latex, 22 pages, including 5 figure
- …