PoS - Proceedings of Science
Volume 444 - 38th International Cosmic Ray Conference (ICRC2023) - Gamma-ray Astronomy (GA)
Probing Gamma-Ray Propagation at Very-High Energies with H.E.S.S. Observations of M87
R. Cecil
Full text: pdf
Pre-published on: August 18, 2023
Published on:
The radio galaxy Messier 87 has an active galactic nucleus, from which observations have been
made of very high energy (E > 100 GeV) 𝛾-rays up to a few 10s of TeV using the H.E.S.S.
telescope array. During monitoring campaigns and target of opportunity observations, several
high flux states could be identified. The high photon statistics obtained during these states allow
us to probe phenomena affecting VHE 𝛾-ray propagation across cosmic distances. Interaction of
these photons with the Extragalactic Background Light (EBL) causes an attenuation, leading to an
observed cut-off in the spectra of very high energy sources. Observations of M87 can be utilized
to make measurements of the local EBL, specifically in the far infrared range. Furthermore, M87
is located at the heart of the nearby Virgo galaxy cluster located 18 Mpc away which is host to
an intra-cluster magnetic field calculated at 34.2 𝜇G. This allows us the opportunity to probe for
effects of the mixing of light pseudo-scalar Axion Like Particles (ALPs) with photon states. These
dark matter candidates are predicted to exhibit an oscillation effect in the presence of magnetic
fields, oscillating between photon and ALP states. This energy-dependent effect would lead to
the disappearance of photons, which would result in measurable “wiggles" in the source’s spectra.
We find that the collected photon statistics do not suffice to significantly detect or constrain the
ALP-photon coupling.
DOI: https://doi.org/10.22323/1.444.0908
How to cite

Metadata are provided both in "article" format (very similar to INSPIRE) as this helps creating very compact bibliographies which can be beneficial to authors and readers, and in "proceeding" format which is more detailed and complete.

Open Access
Creative Commons LicenseCopyright owned by the author(s) under the term of the Creative Commons Attribution-NonCommercial-NoDerivatives 4.0 International License.