On detecting oscillations of gamma rays into axion-like particles in turbulent and coherent magnetic fields
2014 (English)In: Journal of Cosmology and Astroparticle Physics, ISSN 1475-7516, no 9, 003- p.Article in journal (Refereed) Published
Background radiation fields pervade the Universe, and above a certain energy any gamma-ray flux emitted by an extragalactic source should be attenuated due to e(+)e(-) pair production. The opacity could be alleviated if photons oscillated into hypothetical axion-like particles (ALPs) in ambient magnetic fields, leading to a gamma-ray excess especially at high optical depths that could be detected with imaging air Cherenkov telescopes (IACTs). Here, we introduce a method to search for such a signal in gamma-ray data and to estimate sensitivities for future observations. Different magnetic fields close to the gamma-ray source are taken into account in which photons can convert into ALPs that then propagate unimpeded over cosmological distances until they re-convert in the magnetic field of the Milky Way. Specifically, we consider the coherent field at parsec scales in a blazar jet as well as the turbulent field inside a galaxy cluster. For the latter, we explicitly derive the transversal components of a magnetic field with gaussian turbulence which are responsible for the photonALP mixing. To illustrate the method, we apply it to a mock TACT array with characteristics similar to the Cherekov Telescope Array and investigate the dependence of the sensitivity to detect a gamma-ray excess on the magnetic-field parameters.
Place, publisher, year, edition, pages
2014. no 9, 003- p.
gamma ray experiments, active galactic nuclei, magnetic fields, galaxy clusters
Astronomy, Astrophysics and Cosmology
IdentifiersURN: urn:nbn:se:su:diva-108727DOI: 10.1088/1475-7516/2014/09/003ISI: 000342642500004OAI: oai:DiVA.org:su-108727DiVA: diva2:760643