Search for photon-linelike signatures from dark matter annihilations with H.E.S.S

Gamma-ray line signatures can be expected in the very-high-energy (Eγ>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 γ-ray sources that in most cases produce continuous spectra that span over several orders of magnitude in energy. Using data collected with the H.E.S.S. γ-ray instrument, upper limits on linelike 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 γ-ray line emission, flux limits of (2×10⁻⁷–2×10⁻⁵) m⁻² s⁻1 sr⁻1 and (1×10⁻⁸–2×10⁻⁶) 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 ⟨σv⟩χχ→γγ reach ∼10⁻²⁷ cm³ s⁻¹, based on the Einasto parametrization of the Galactic DM halo density profile.A. Abramowski ... P. de Wilt ... N. Maxted ... B. Nicholas ... G. Rowell ... et al. (H.E.S.S. Collaboration