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

Abstract

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.