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

摘要

The Sculptor and Carina Dwarf spheroidal galaxies were observed with the H.E.S.S. Cherenkov telescope arraybetween 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 distributionare obtained at the level of 10-13to 10-12cm-2s-1 in the TeV range for power law and dark matter annihilation spectralenergy distributions. Constraints on dark matter particle velocity weighted annihilation cross section for both Sculptorand Carina dwarf galaxies range from 10-21cm3s-1down to 10-22cm3s-1depending on the darkmatter halo model halo modelling. 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 matterhalo distributions.