hide
Free keywords:
Astrophysics, High Energy Astrophysical Phenomena, astro-ph.HE
MPINP:
HESS - Abteilung Hinton
Abstract:
Dwarf spheroidal galaxy satellites of the Milky Way are prime targets for
indirect detection of dark matter with gamma rays due to their proximity, high
dark matter content and absence of non-thermal emission processes. Recently,
the Dark Energy Survey (DES) revealed the existence of new ultra-faint dwarf
spheroidal galaxies in the southern-hemisphere sky, therefore ideally located
for ground-based observations with the imaging atmospheric Cherenkov telescope
array H.E.S.S. We present a search for very-high-energy ($E\gtrsim100$ GeV)
gamma-ray emission using H.E.S.S. observations carried out recently towards
Reticulum II, Tucana II, Tucana III, Tucana IV and Grus II satellites. No
significant very-high-energy gamma-ray excess is found from the observations on
any individual object nor in the combined analysis of all the datasets. Using
the most recent modeling of the dark matter distribution in the dwarf galaxy
halo, we compute for the first time on DES satellites individual and combined
constraints from Cherenkov telescope observations on the annihilation cross
section of dark matter particles in the form of Weakly Interacting Massive
Particles. The combined 95% C.L. observed upper limits reach $\langle \sigma v
\rangle \simeq 1 \times 10^{-23}$ cm$^3$s$^{-1}$ in the $W^+W^-$ channel and $4
\times 10^{-26}$ cm$^3$s$^{-1}$ in the $\gamma\gamma$ channels for a dark
matter mass of 1.5 TeV. The H.E.S.S. constraints well complement the results
from Fermi-LAT, HAWC, MAGIC and VERITAS and are currently the most stringent in
the $\gamma\gamma$ channels in the multi-GeV/multi-TeV mass range.
