On detecting oscillations of gamma rays into axion-like particles in turbulent and coherent magnetic fields
- The Oskar Klein Center for CosmoParticle Physics, Department of Physics, Stockholm University, Albanova, SE-10691 Stockholm (Sweden)
- Dipartimento di Matematica e Fisica ''Ennio De Giorgi'', Università del Salento and INFN—Sezione di Lecce, Via Arnesano, I-73100 Lecce (Italy)
Background radiation fields pervade the Universe, and above a certain energy any γ-ray flux emitted by an extragalactic source should be attenuated due to e{sup +}e{sup -} pair production. The opacity could be alleviated if photons oscillated into hypothetical axion-like particles (ALPs) in ambient magnetic fields, leading to a γ-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 γ-ray data and to estimate sensitivities for future observations. Different magnetic fields close to the γ-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 photon-ALP mixing. To illustrate the method, we apply it to a mock IACT array with characteristics similar to the Cherekov Telescope Array and investigate the dependence of the sensitivity to detect a γ-ray excess on the magnetic-field parameters.
- OSTI ID:
- 22375902
- Journal Information:
- Journal of Cosmology and Astroparticle Physics, Vol. 2014, Issue 09; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 1475-7516
- Country of Publication:
- United States
- Language:
- English
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