Boltzmann approach to the large-angle cosmic X-ray background fluctuations

Large-angle fluctuations in the cosmic X-ray background are investigated by a new formalism with a simple model of the X-ray sources. Our method is formulated from the Boltzmann equation and a simple extension of the work by Lahav et al. to be applicable to a hyperbolic (open) universe. The low mult...

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Bibliographic Details
Published in:arXiv.org 1998-05
Main Authors: Miura, Yasuhiro, Yamamoto, Kazuhiro, Miyauchi, Kenta, Hosonuma, Masayasu
Format: Article
Language:English
Subjects:
Astronomical models
Background radiation
Boltzmann transport equation
Clustering
Cosmology
Dipole moments
Elastic scattering
Multipoles
Universe
Variation
X ray sources
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Summary:Large-angle fluctuations in the cosmic X-ray background are investigated by a new formalism with a simple model of the X-ray sources. Our method is formulated from the Boltzmann equation and a simple extension of the work by Lahav et al. to be applicable to a hyperbolic (open) universe. The low multipole fluctuations due to the source clustering are analyzed in various cosmological models in both numerical and analytic way. The fluctuations strongly depend on the X-ray sources evolution model, as pointed out previously. It turns out that the nearby (\(z \lesssim 0.1\)) sources are the dominant contributors to the large-angle fluctuations. If these nearby sources are removed in an observed X-ray map, the dipole (low multipole) moment of the fluctuation drastically decreases. In this case the Compton-Getting effect of an observer's motion can be a dominant contribution to the dipole fluctuation. This feature of fluctuation, relating to the matter power spectrum, is discussed.
ISSN:2331-8422
DOI:10.48550/arxiv.9805168