Dwarf spheroidal galaxies of the Local Group are close satellites of the Milky Way characterized by a large mass-to-light ratio and are not expected to be the site of non-thermal high-energy gamma-ray emission or intense star formation .
Therefore they are amongst the most promising candidates for indirect dark matter searches .
During the last years the High Energy Stereoscopic System ( H.E.S.S . )
of imaging atmospheric Cherenkov telescopes observed five of these dwarf galaxies for more than 140 hours in total , searching for TeV gamma-ray emission from annihilation of dark matter particles .
The new results of the deep exposure of the Sagittarius dwarf spheroidal galaxy , the first observations of the Coma Berenices and Fornax dwarves and the re-analysis of two more dwarf spheroidal galaxies already published by the H.E.S.S .
Collaboration , Carina and Sculptor , are presented .
In the absence of a significant signal new constraints on the annihilation cross-section applicable to Weakly Interacting Massive Particles ( WIMPs ) are derived by combining the observations of the five dwarf galaxies .
The combined exclusion limit depends on the WIMP mass and the best constraint is reached at 1–2 TeV masses with a cross-section upper bound of \sim 3.9 \times 10 ^ { -24 } cm ^ { 3 } s ^ { -1 } at a 95 \% confidence level .