  We study observable signals from dark matter that self-annihilates via
Sommerfeld effect in dwarf spheroidal galaxies (dSphs). Since the effect of the
Sommerfeld enhancement depends on the velocity of dark matter, it is crucial to
determine the profile of dSphs to compute the J-factor, i.e., the line-of-sight
integral of density squared. In our study we use the prior distributions of the
parameters for satellite density profiles in order to determine the J-factor,
making most out of the recent developments in the N-body simulations and
semi-analytical modeling for the structure formation. As concrete model, we
analyze fermionic dark matter that annihilates via a light scalar and Wino dark
matter in supersymmetric models. We find that, with the more realistic prior
distributions that we adopt in this study, the J-factor of the most promising
dwarf galaxies is decreased by a factor of a few, compared with earlier
estimates based on non-informative priors. Nevertheless, the Cherenkov
Telescope Array should be able to detect thermal Wino dark matter by pointing
it toward best classical or ultrafaint dwarf galaxies for 500 hours.
