The Milky Way as a Kiloparsec-Scale Axionscope

By M. Simet, D. Hooper, P. Serpico. 2007

183 citations recorded by the source corpus.

Very high energy gamma-rays are expected to be absorbed by the extragalactic background light over cosmological distances via the process of electron-positron pair production. Recent observations of cosmologically distant gamma-ray emitters by ground based gamma-ray telescopes have, however, revealed a surprising degree of transparency of the universe to very high energy photons. One possible mechanism to explain this observation is the oscillation between photons and axion-like-particles (ALPs). Here we explore this possibility further, focusing on photon-ALP conversion in the magnetic fields in and around gamma-ray sources and in the magnetic field of the Milky Way, where some fraction of the ALP flux is converted back into photons. We show that this mechanism can be efficient in allowed regions of the ALP parameter space, as well as in typical configurations of the Galactic Magnetic Field. As case examples, we consider the spectrum observed from two HESS sources: 1ES1101-232 at redshift z = 0.186 and H 2356-309 at z = 0.165. We also discuss features of this scenario which could be used to distinguish it from standard or other exotic models.

Subfields: Nuclear and High Energy Physics

View Paper: https://www.semanticscholar.org/paper/485256c3e48487bd7705aeb805ca0fc6f46b0452

How researchers see this paper

The researchers whose trusted networks rank it highest, strongest advocate first. Every researcher gets a different order.

In Nuclear and High Energy Physics

Citations in the corpus

The type IIB string axiverse and its low-energy phenomenology (2012, background): “tantalising astrophysical hints, which together point to a light ALP with couplings and mass [7–12]:”
Exploring the Role of Axions and Other WISPs in the Dark Universe (2012, unknown): “10 −9 eV, ALP, which couples to two photons with strength [62, 63, 64, 65], giγ ∼ 10 GeV ⇒ fai/Ciγ ∼ 10(8) GeV.”
Revisiting the SN1987A gamma-ray limit on ultralight axion-like particles (2014, background): “In particular, an intriguing hint for these particles has been recently suggested by veryhigh-energy gamma-ray experiments: in fact, photon–ALP conversions in large-scale cosmic magnetic fields would modify the opacity of the universe to TeV photons and this might explain an anomalous spectral harde”
Towards a new generation axion helioscope (2011, background): “Photon-ALP conversion has been invoked by a number of authors [61–66] to account for these observations via a photon regeneration effect.”
Dark matter and fundamental physics with the Cherenkov Telescope Array (2012, methodology): “ [137], but it could also have important implications for astronomical observations. For example, photon/ALP mixing could distort the spectra of gamma-raysources, such as Active Galactic Nuclei (AGN) [138, 139, 140, 141] or galactic sources, in the TeV range [142]. The photon/ALP mixing eﬀect for di”
Indications for a pair-production anomaly from the propagation of VHE gamma-rays (2012, unknown): “In the most general form, mixing during propagation in the intergalactic medium with a given domain size [16, 17] would have to be combined with mixing in the source [23] and the Galactic magnetic field [76].”
A new interpretation of the gamma-ray observations of distant active galactic nuclei (2009, background): “Among other proposed explanations, it was suggested that photons may convert into some hypothetical axion-like particles that convert back into photons in the galactic magnetic fields [9, 10], or that Lorentz invariance violation may be the reason for the lack of absorption [11].”