On the effect of cyclotron emission on the spectral distortions of the cosmic microwave background

Abstract

We have investigated the role of the cyclotron emission associated to cosmic magnetic fields on the evolution of CMB spectral distortions by considering the contributions by spontaneous and stimulated emission and by absorption in the computation of the photon and energy injection rates. These cyclotron emission rates have been numerically compared with those of the relevant radiative processes operating in the cosmic plasma, bremsstrahlung and double Compton scattering, for realistic CMB distorted spectra at early and late epochs. For reasonable magnetic field strengths we find that the cyclotron emission contribution is much smaller than the bremsstrahlung and double Compton contributions, because of their different frequency locations and the high bremsstrahlung and double Compton efficiency to keep the long wavelength region of the CMB spectrum close to a blackbody (at electron temperature) during the formation of the spectral distortion. Differently from previous analyses, we find that for a very large set of dissipation mechanisms the role of cyclotron emission in the evolution of CMB spectral distortions is negligible and, in particular, it cannot re-establish a blackbody spectrum after the generation of a realistic early distortion. The constraints on the energy exchanges at various cosmic times can be then derived, under quite general assumptions, by considering only Compton scattering, bremsstrahlung, and double Compton, other than, obviously, the considered dissipation process. Finally, upper limits to the CMB polarization degree induced by cyclotron emission have been estimated.

41 pages, 7 figures. Submitted to New Astronomy: December, 6, 2004 ; in this revised form: April, 28, 2005; accepted: May, 9, 2005

References in corpus (4)

• First Year Wilkinson Microwave Anisotropy Probe (WMAP) Observations: Preliminary Maps and Basic Results
• The Origin and Evolution of Cosmic Magnetism
• Small-scale CMB polarization anisotropies due to tangled primordial magnetic fields
• What can we learn on the thermal history of the Universe from future CMB spectrum measures at long wavelengths?

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• Semi-analytical description of clumping factor and CMB free-free distortions from reionization
• Probing large-scale magnetism with the Cosmic Microwave Background
• A numerical code for the solution of the Kompaneets equation in cosmological context
• On a possible nonequilibrium imprint in the cosmic background at low frequencies
• Cyclotron emission effect on CMB spectral distortions