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 h and 14.8 h 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% CL 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 10-13-10-12 cm-2 s-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 〈σv〉 ∼ 10-21 cm3 s-1 down to 〈σv〉 ∼ 10-22 cm3 s -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.
|Original language||English (US)|
|Number of pages||9|
|State||Published - Mar 2011|
Bibliographical noteFunding Information:
The authors thank Mark Wilkinson for fruitful discussions concerning the modelling of Carina dSph. The support of the Namibian authorities and of the University of Namibia in facilitating the construction and operation of H.E.S.S. is gratefully acknowledged, as is the support by the German Ministry for Education and Research (BMBF) , the Max Planck Society , the French Ministry for Research , the CNRS-IN2P3 and the Astroparticle Interdisciplinary Programme of the CNRS , the UK Particle Physics and Astronomy Research Council (PPARC) , the IPNP of the Charles University , the South African Department of Science and Technology and National Research Foundation , and by the University of Namibia . We appreciate the excellent work of the technical support staff in Berlin, Durham, Hamburg, Heildelberg, Palaiseau, Paris, Saclay, and in Namibia in the construction and operation of the equipment.
- Dark matter
- Gamma-rays: observations - Dwarf spheroidal galaxy
- Internal Bremsstrahlung
- Sommerfeld enhancement