H.E.S.S. constraints on Dark Matter annihilations towards the Sculptor and Carina Dwarf Galaxies

TL;DR

This study used H.E.S.S. telescope observations of the Sculptor and Carina dwarf galaxies to set upper limits on gamma-ray fluxes and dark matter annihilation cross sections, constraining dark matter models.

Contribution

First to provide gamma-ray flux upper limits and dark matter annihilation constraints for these dwarf galaxies using H.E.S.S. data.

Findings

No gamma-ray signals detected above 220-320 GeV.

Upper limits on gamma-ray fluxes are set at 10^-13 to 10^-12 cm^-2s^-1.

Constraints on dark matter annihilation cross sections range from 10^-21 to 10^-22 cm^3s^-1.

Abstract

The Sculptor and Carina Dwarf spheroidal galaxies were observed with the H.E.S.S. Cherenkov telescope array between January 2008 and December 2009. The data sets consist of a total of 11.8 and 14.8 hours of high quality data, respectively. No gamma-ray signal was detected at the nominal positions of these galaxies above 220 GeV and 320 GeV, respectively. Upper limits on the gamma-ray fluxes at 95% C.L. assuming two forms for the spectral energy distribution (a power law shape and one derived from dark matter annihilation) are obtained at the level of 10^-13 to 10^-12 cm^-2s^-1 in the TeV range. Constraints on the velocity weighted dark matter particle annihilation cross section for both Sculptor and Carina dwarf galaxies range from <\sigma v> ~ 10^-21 cm^3s^-1 down to <\sigma v> ~ 10^-22 cm^3s^-1 depending on the dark matter halo model used. Possible enhancements of the gamma-ray flux are studied: the Sommerfeld effect, which is found to exclude some dark matter particle masses, the internal Bremsstrahlung and clumps in the dark-matter halo distributions.