Search for photon line-like signatures from Dark Matter annihilations with H.E.S.S

TL;DR

This study used H.E.S.S. gamma-ray data to search for dark matter annihilation signatures in the form of gamma-ray lines, setting upper limits on such signals across a broad energy range and constraining dark matter properties.

Contribution

First to set comprehensive upper limits on gamma-ray line signatures from dark matter using H.E.S.S. data in the 500 GeV to 25 TeV range, complementing Fermi-LAT results at lower energies.

Findings

No significant gamma-ray line signals detected.

Established flux upper limits for line emission at various energies.

Constrained dark matter annihilation cross section to ~10^-27 cm^3 s^-1 for 1 TeV mass.

Abstract

Gamma-ray line signatures can be expected in the very-high-energy (VHE; E_\gamma > 100 GeV) domain due to self-annihilation or decay of dark matter (DM) particles in space. Such a signal would be readily distinguishable from astrophysical \gamma-ray sources that in most cases produce continuous spectra which span over several orders of magnitude in energy. Using data collected with the H.E.S.S. \gamma-ray instrument, upper limits on line-like emission are obtained in the energy range between ~500 GeV and ~25 TeV for the central part of the Milky Way halo and for extragalactic observations, complementing recent limits obtained with the Fermi-LAT instrument at lower energies. No statistically significant signal could be found. For monochromatic \gamma-ray line emission, flux limits of (2x10^-7 - 2x10^-5) m^-2 s^-1 sr^-1 and (1x10^-8 - 2x10^-6) m^-2 s^-1 sr^-1 are obtained for the central part of the Milky Way halo and extragalactic observations, respectively. For a DM particle mass of 1 TeV, limits on the velocity-averaged DM annihilation cross section < \sigma v >(\chi\chi -> \gamma\gamma) reach ~10^-27 cm^3 s^-1, based on the Einasto parametrization of the Galactic DM halo density profile.