A search for dark matter in Triangulum II with the MAGIC telescopes

Abstract We present the first results from very-high-energy observations of the dwarf spheroidal satellite candidate Triangulum II with the MAGIC telescopes from 62.4 h of good-quality data taken between August 2016 and August 2017. We find no gamma-ray excess in the direction of Triangulum II, and upper limits on both the differential and integral gamma-ray flux are presented. Currently, the kinematics of Triangulum II are affected by large uncertainties leading to a bias in the determination of the properties of its dark matter halo. Using a scaling relation between the annihilation J-factor and heliocentric distance of well-known dwarf spheroidal galaxies, we estimate an annihilation J-factor for Triangulum II for WIMP dark matter of log [ J ann ( 0 . 5 ° ) ∕ GeV 2 cm − 5 ] = 19 . 35 ± 0 . 37 . We also derive a dark matter density profile for the object relying on results from resolved simulations of Milky Way sized dark matter halos. We obtain 95% confidence-level limits on the thermally averaged annihilation cross section for WIMP annihilation into various Standard Model channels. The most stringent limits are obtained in the τ − τ + final state, where a cross section for annihilation down to 〈 σ ann v 〉 = 3 . 05 × 1 0 − 24  cm3 s−1 is excluded.