Predictions of the Angular Power Spectrum of Clustered Extragalactic Point Sources at Cosmic Microwave Background Frequencies from Flat and All‐Sky Two‐dimensional Simulations

2005 ◽  
Vol 621 (1) ◽  
pp. 1-14 ◽  
Author(s):  
J. Gonzalez‐Nuevo ◽  
L. Toffolatti ◽  
F. Argueso
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Point Sources ◽  
Two Dimensional ◽  
Microwave Background ◽  
Angular Power Spectrum

A Measurement by BOOMERANG of Multiple Peaks in the Angular Power Spectrum of the Cosmic Microwave Background

2002 ◽  
Vol 571 (2) ◽  
pp. 604-614 ◽  
Author(s):  
C. B. Netterfield ◽  
P. A. R. Ade ◽  
J. J. Bock ◽  
J. R. Bond ◽  
J. Borrill ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Multiple Peaks

scholarly journals Unexpected topology of the temperature fluctuations in the cosmic microwave background

2019 ◽  
Vol 627 ◽  
pp. A163 ◽  
Author(s):  
Pratyush Pranav ◽  
Robert J. Adler ◽  
Thomas Buchert ◽  
Herbert Edelsbrunner ◽  
Bernard J. T. Jones ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Euler Characteristic ◽  
Betti Numbers ◽  
Temperature Fluctuations ◽  
Point Sources ◽  
Anomalous Behaviour ◽  
Topological Descriptors ◽  
Microwave Background ◽  
Number Of Components

We study the topology generated by the temperature fluctuations of the cosmic microwave background (CMB) radiation, as quantified by the number of components and holes, formally given by the Betti numbers, in the growing excursion sets. We compare CMB maps observed by the Planck satellite with a thousand simulated maps generated according to the ΛCDM paradigm with Gaussian distributed fluctuations. The comparison is multi-scale, being performed on a sequence of degraded maps with mean pixel separation ranging from 0.05 to 7.33°. The survey of the CMB over 𝕊2 is incomplete due to obfuscation effects by bright point sources and other extended foreground objects like our own galaxy. To deal with such situations, where analysis in the presence of “masks” is of importance, we introduce the concept of relative homology. The parametric χ2-test shows differences between observations and simulations, yielding p-values at percent to less than permil levels roughly between 2 and 7°, with the difference in the number of components and holes peaking at more than 3σ sporadically at these scales. The highest observed deviation between the observations and simulations for b0 and b1 is approximately between 3σ and 4σ at scales of 3–7°. There are reports of mildly unusual behaviour of the Euler characteristic at 3.66° in the literature, computed from independent measurements of the CMB temperature fluctuations by Planck’s predecessor, the Wilkinson Microwave Anisotropy Probe (WMAP) satellite. The mildly anomalous behaviour of the Euler characteristic is phenomenologically related to the strongly anomalous behaviour of components and holes, or the zeroth and first Betti numbers, respectively. Further, since these topological descriptors show consistent anomalous behaviour over independent measurements of Planck and WMAP, instrumental and systematic errors may be an unlikely source. These are also the scales at which the observed maps exhibit low variance compared to the simulations, and approximately the range of scales at which the power spectrum exhibits a dip with respect to the theoretical model. Non-parametric tests show even stronger differences at almost all scales. Crucially, Gaussian simulations based on power-spectrum matching the characteristics of the observed dipped power spectrum are not able to resolve the anomaly. Understanding the origin of the anomalies in the CMB, whether cosmological in nature or arising due to late-time effects, is an extremely challenging task. Regardless, beyond the trivial possibility that this may still be a manifestation of an extreme Gaussian case, these observations, along with the super-horizon scales involved, may motivate the study of primordial non-Gaussianity. Alternative scenarios worth exploring may be models with non-trivial topology, including topological defect models.

A Measurement of the Angular Power Spectrum of the Cosmic Microwave Background from [CLC][ITAL]l[/ITAL][/CLC] = 100 to 400

1999 ◽  
Vol 524 (1) ◽  
pp. L1-L4 ◽  
Author(s):  
A. D. Miller ◽  
R. Caldwell ◽  
M. J. Devlin ◽  
W. B. Dorwart ◽  
T. Herbig ◽  
...  
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Microwave Background ◽  
Angular Power Spectrum

scholarly journals The polarimetric multi-frequency radio sources properties

2016 ◽  
Vol 25 (11) ◽  
pp. 1640005 ◽  
Author(s):  
Vincenzo Galluzzi ◽  
Marcella Massardi
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
State Of The Art ◽  
The State ◽  
Radio Sources ◽  
Microwave Background ◽  
Complete Sample ◽  
Angular Power Spectrum ◽  
Extragalactic Radio Sources ◽  
Compact Array

The polarization properties of extragalactic radio sources at frequencies higher than [Formula: see text]GHz are still poorly constrained. However, their characterization would provide invaluable information about the physics of the emission processes and is crucial to estimate their contamination as foregrounds of the polarized Cosmic Microwave Background (CMB) angular power spectrum on scales [Formula: see text]arcmin. In this contribution, after summarizing the state-of-the-art of polarimetric observations in the millimetric wavelength bands, we present our observations of a complete sample of 53 sources with [Formula: see text]mJy carried out with the Australia Telescope Compact Array (ACTA) between [Formula: see text] and [Formula: see text]GHz. The analysis clearly shows that polarization properties cannot be simply inferred from total intensity ones, as the spectral behaviors of the two signals are typically different.

scholarly journals Cosmic Strings and Their Induced Non-Gaussianities in the Cosmic Microwave Background

2010 ◽  
Vol 2010 ◽  
pp. 1-28 ◽  
Author(s):  
Christophe Ringeval
Keyword(s):  
Power Spectrum ◽  
Cosmic Microwave Background ◽  
Early Universe ◽  
Cosmic Strings ◽  
Point Function ◽  
Microwave Background ◽  
Angular Power Spectrum ◽  
Gravitational Perturbations ◽  
The One ◽  
Non Gaussian

Motivated by the fact that cosmological perturbations of inflationary quantum origin were born Gaussian, the search for non-Gaussianities in the cosmic microwave background (CMB) anisotropies is considered as the privileged probe of nonlinear physics in the early universe. Cosmic strings are active sources of gravitational perturbations and incessantly produce non-Gaussian distortions in the CMB. Even if, on the currently observed angular scales, they can only contribute a small fraction of the CMB angular power spectrum, cosmic strings could actually be the main source of its non-Gaussianities. In this paper, after having reviewed the basic cosmological properties of a string network, we present the signatures Nambu-Goto cosmic strings would induce in various observables ranging from the one-point function of the temperature anisotropies to the bispectrum and trispectrum. It is shown that string imprints are significantly different than those expected from the primordial type of non-Gaussianity and could therefore be easily distinguished.

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