49 research outputs found
On the detection of point sources in Planck LFI 70 GHz CMB maps based on cleaned K-map
We use the Planck LFI 70GHz data to further probe point source detection
technique in the sky maps of the cosmic microwave background (CMB) radiation.
The method developed by Tegmark et al. for foreground reduced maps and the
Kolmogorov parameter as the descriptor are adopted for the analysis of Planck
satellite CMB temperature data. Most of the detected points coincide with point
sources already revealed by other methods. However, we have also found 9 source
candidates for which still no counterparts are known.Comment: 11 pages, 3 figures, Accepted for publication in Modern Physics
Letters A. arXiv admin note: substantial text overlap with arXiv:1206.712
Probing the statistic in the cosmic microwave background
Kolmogorov's statistic is used for the analysis of properties of
perturbations in the Cosmic Microwave Background signal. We obtain the maps of
the Kolmogorov stochasticity parameter for W and V band temperature data of
WMAP which are differently affected by the Galactic disk radiation and then we
model datasets with various statistic of perturbations. The analysis shows that
the Kolmogorov's parameter can be an efficient tool for the separation of
Cosmic Microwave Background from the contaminating radiations due to their
different statistical properties.Comment: 6 pages, 4 figure
Hubble Diagram of Gamma-Rays Bursts calibrated with Gurzadyan-Xue Cosmology
Gamma-ray bursts (GRBs) being the most luminous among known cosmic objects
carry an essential potential for cosmological studies if properly used as
standard candles. In this paper we test with GRBs the cosmological predictions
of the Gurzadyan-Xue (GX) model of dark energy, a novel theory that predicts,
without any free parameters, the current vacuum fluctuation energy density
close to the value inferred from the SNIa observations. We also compare the GX
results with those predicted by the concordance scenario -CDM.
According to the statistical approach by Schaefer (2007), the use of several
empirical relations obtained from GRBs observables, after a consistent
calibration for a specific model, enables one to probe current cosmological
models. Based on this recently introduced method, we use the 69 GRBs sample
collected by Schaefer (2007); and the most recently released SWIFT satellite
data (Sakamoto et al. 2007) together with the 41 GRBs sample collected by
Rizzuto et al. (2007), which has the more firmly determined redshifts. Both
data samples span a distance scale up to redshift about 7. We show that the GX
models are compatible with the Hubble diagram of the Schaefer (2007) 69 GRBs
sample. Such adjustment is almost identical to the one for the concordance
-CDM.Comment: 9 pages, 17 figures, 11 tables; Astr. & Astrophys. (in press
To the center of cold spot with Planck
The structure of the cold spot, of a non-Gaussian anomaly in the cosmic
microwave background (CMB) sky first detected by Vielva et al. is studied using
the data by Planck satellite. The obtained map of the degree of stochasticity
(K-map) of CMB for the cold spot, reveals, most clearly in 100 GHz band, a
shell-type structure with a center coinciding with the minima of the
temperature distribution. The shell structure is non-Gaussian at a 4\sigma
confidence level. Such behavior of the K-map supports the void nature of the
cold spot. The applied method can be used for tracing voids that have no
signatures in redshift surveys.Comment: A & A (in press), 4 pages, 5 figures; to match the published versio