Prospects for a Dark Matter Annihilation Signal toward the Sagittarius Dwarf Galaxy with Ground-based Cherenkov telescopes

Viana, A.; Medina, M. C.; Peñarrubia, J.; Brun, P.; Glicenstein, J. F.; Kosack, K.; Moulin, E.; Naumann-Godo, M.; Peyaud, B.
The Astrophysical Journal, Volume 746, Issue 1, article id. 77, 7 pp. (2012).


Dwarf galaxies are widely believed to be among the best targets for indirect dark matter searches using high-energy gamma rays and indeed gamma-ray emission from these objects has long been a subject of detailed study for ground-based atmospheric Cherenkov telescopes. Here, we update current exclusion limits obtained on the closest dwarf, the Sagittarius dwarf galaxy, in light of recent realistic dark matter halo models. The constraints on the velocity-weighted annihilation cross-section of the dark matter particle are of a few 10-23 cm3 s-1 in the TeV energy range for a 50 hr exposure. The limits are extrapolated to the sensitivities of future Cherenkov Telescope Arrays. For 200 hr of observation time, the sensitivity at the 95% confidence level reaches 10-25 cm3 s-1. Possible astrophysical backgrounds from gamma-ray sources dissembled in the Sagittarius dwarf are studied. It is shown that with long enough observation times, gamma-ray background from millisecond pulsars in a globular cluster contained within the Sagittarius dwarf may limit the sensitivity to dark matter annihilations.