Actions for Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources [electronic resource].

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Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources [electronic resource].

Published
Washington, D.C. : United States. Dept. of Energy. Office of Science, 2009.
Oak Ridge, Tenn. : Distributed by the Office of Scientific and Technical Information, U.S. Dept. of Energy.
Physical Description
16 pages : digital, PDF file
Additional Creators
SLAC National Accelerator Laboratory, United States. Department of Energy. Office of Science, and United States. Department of Energy. Office of Scientific and Technical Information
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Summary
Axion Like Particles (ALPs) are predicted to couple with photons in the presence of magnetic fields. This effect may lead to a significant change in the observed spectra of gamma-ray sources such as AGNs. Here we carry out a detailed study that for the first time simultaneously considers in the same framework both the photon/axion mixing that takes place in the gamma-ray source and that one expected to occur in the intergalactic magnetic fields. An efficient photon/axion mixing in the source always means an attenuation in the photon flux, whereas the mixing in the intergalactic medium may result in a decrement and/or enhancement of the photon flux, depending on the distance of the source and the energy considered. Interestingly, we find that decreasing the value of the intergalactic magnetic field strength, which decreases the probability for photon/axion mixing, could result in an increase of the expected photon flux at Earth if the source is far enough. We also find a 30% attenuation in the intensity spectrum of distant sources, which occurs at an energy that only depends on the properties of the ALPs and the intensity of the intergalactic magnetic field, and thus independent of the AGN source being observed. Moreover, we show that this mechanism can easily explain recent puzzles in the spectra of distant gamma-ray sources, like the possible detection of TeV photons from 3C 66A (a source located at z=0.444) by MAGIC and VERITAS, which should not happen according to conventional models of photon propagation over cosmological distances. Another puzzle is the recent published lower limit to the EBL intensity at 3.6 {micro}m (which is almost twice larger as the previous one), which implies very hard spectra for some detected TeV gamma-ray sources located at z=0.1-0.2. The consequences that come from this work are testable with the current generation of gamma-ray instruments, namely Fermi (formerly known as GLAST) and imaging atmospheric Cherenkov telescopes like CANGAROO, HESS, MAGIC and VERITAS.
Report Numbers
E 1.99:slac-pub-13647
slac-pub-13647
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Note
Published through SciTech Connect.
06/23/2009.
"slac-pub-13647"
"arXiv:0905.3270"
Phys.Rev.D79:123511,2009 79 12 ISSN 1550--7998 FT
Prada, F.; Paneque, D.; Bloom, E.; Dominguez, A.; Sanchez-Conde, M.A.
Funding Information
AC02-76SF00515
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