Observations of the Sagittarius dwarf galaxy by the HESS experiment and search for a dark matter signal

Abstract

Observations of the Sagittarius dwarf spheroidal (Sgr dSph) galaxy were carried out with the HESS array of four imaging air Cherenkov telescopes in June 2006. A total of 11 h of high quality data are available after data selection. There is no evidence for a very high energy γ-ray signal above the energy threshold at the target position. A 95% CL flux limit of 3.6 × 10 - 12 cm - 2 s - 1 above 250 GeV has been derived. Constraints on the velocity-weighted cross-section 〈 σ v 〉 are calculated in the framework of dark matter particle annihilation using realistic models for the dark matter halo profile of Sagittarius dwarf galaxy. Two different models have been investigated encompassing a large class of halo types. A 95% CL exclusion limit on 〈 σ v 〉 of the order of 2 × 10 - 25 cm 3 s - 1 is obtained for a core profile in the 100 GeV–1 TeV neutralino mass range.