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

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 gamma-ray signal above the energy threshold at the target position. A 95% CL flux limit of 3.6 x 10(-12) cm(-2) s(-1) above 250 GeV has been derived. Constraints on the velocity-weighted cross-section (sigma upsilon) 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 (sigma upsilon) of the order of 2 x 10(-25) cm(3) s(-1) is obtained for a core profile in the 100 GeV-1 TeV neutralino mass range. (c) 2007 Elsevier B.V. All rights reserved.