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Photon-axion mixing within the jets of active galactic nuclei and prospects for detection.

Harris, J. and Chadwick, P.M. (2014) 'Photon-axion mixing within the jets of active galactic nuclei and prospects for detection.', Journal of cosmology and astroparticle physics., 2014 (10). 018.


Very high energy γ-ray observations of distant active galactic nuclei (AGN) generally result in higher fluxes and harder spectra than expected, resulting in some tension with the level of the extragalactic background light (EBL). If hypothetical axions or axion-like particles (ALPs) were to exist, this tension could be relieved since the oscillation of photons to ALPs would mitigate the effects of EBL absorption and lead to softer inferred intrinsic AGN spectra. In this paper we consider the effect of photon-ALP mixing on observed spectra, including the photon-ALP mixing that would occur within AGN jets. We then simulate observations of three AGN with the Cherenkov Telescope Array (CTA), a next generation γ-ray telescope, to determine its prospects for detecting the signatures of photon-ALP mixing on the spectra. We conclude that prospects for CTA detecting these signatures or else setting limits on the ALP parameter space are quite promising. We find that prospects are improved if photon-ALP mixing within the jet is properly considered and that the best target for observations is PKS 2155-304.

Item Type:Article
Keywords:Active galactic nuclei, Absorption and radiation processes.
Full text:(NA) Not Applicable
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Publisher statement:This is an author-created, un-copyedited version of an article published in Journal of Cosmology and Astroparticle Physics. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at
Date accepted:03 September 2014
Date deposited:No date available
Date of first online publication:09 October 2014
Date first made open access:No date available

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