Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources

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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 ... continued below

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16 pages

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Sanchez-Conde, M. A.; Paneque, D.; Bloom, E.; Prada, F. & Dominguez, A. June 23, 2009.

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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.

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16 pages

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  • Journal Name: Submitted to Physical Review D and Astrophysical Journal

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  • Report No.: SLAC-PUB-13647
  • Grant Number: AC02-76SF00515
  • Office of Scientific & Technical Information Report Number: 958060
  • Archival Resource Key: ark:/67531/metadc931871

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Office of Scientific & Technical Information Technical Reports

Reports, articles and other documents harvested from the Office of Scientific and Technical Information.

Office of Scientific and Technical Information (OSTI) is the Department of Energy (DOE) office that collects, preserves, and disseminates DOE-sponsored research and development (R&D) results that are the outcomes of R&D projects or other funded activities at DOE labs and facilities nationwide and grantees at universities and other institutions.

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  • June 23, 2009

Added to The UNT Digital Library

  • Nov. 13, 2016, 7:26 p.m.

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  • July 26, 2017, 10:51 a.m.

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Sanchez-Conde, M. A.; Paneque, D.; Bloom, E.; Prada, F. & Dominguez, A. Hints of the Existence of Axion-Like-Particles From the Gamma-Ray Spectra of Cosmological Sources, article, June 23, 2009; United States. (digital.library.unt.edu/ark:/67531/metadc931871/: accessed December 11, 2017), University of North Texas Libraries, Digital Library, digital.library.unt.edu; crediting UNT Libraries Government Documents Department.