Searches for gamma-ray lines and `pure WIMP' spectra from Dark Matter annihilations in dwarf galaxies with H.E.S.S

TL;DR

This study uses H.E.S.S. observations of dwarf galaxies to search for gamma-ray signals indicative of dark matter annihilation, setting limits on annihilation cross sections and constraining pure WIMP models.

Contribution

The paper provides the first H.E.S.S. limits on gamma-ray lines and pure WIMP spectra from dwarf galaxies, analyzing the full spectral shape to constrain dark matter models.

Findings

No gamma-ray signals detected.

Upper limits on annihilation cross section around 3 x 10^{-25} cm^3 s^{-1}.

Excluded some WIMP mass ranges but not the thermal candidates.

Abstract

Dwarf spheroidal galaxies are among the most promising targets for detecting signals of Dark Matter (DM) annihilations. The H.E.S.S. experiment has observed five of these systems for a total of about 130 hours. The data are re-analyzed here, and, in the absence of any detected signals, are interpreted in terms of limits on the DM annihilation cross section. Two scenarios are considered: i) DM annihilation into mono-energetic gamma-rays and ii) DM in the form of pure WIMP multiplets that, annihilating into all electroweak bosons, produce a distinctive gamma-ray spectral shape with a high-energy peak at the DM mass and a lower-energy continuum. For case i), upper limits at 95\% confidence level of about $\langle \sigma v \rangle \lesssim 3 \times 10^{-25}$ cm$^3$ s$^{-1}$ are obtained in the mass range of 400 GeV to 1 TeV. For case ii), the full spectral shape of the models is used and several excluded regions are identified, but the thermal masses of the candidates are not robustly ruled out.