  Stellar abundance pattern of neutron-capture elements such as barium is used
as a powerful tool to infer how star formation proceeded in dwarf spheroidal
(dSph) galaxies. It is found that the abundance correlation of barium with iron
in stars belonging to dSph galaxies orbiting the Milky Way, i.e., Draco,
Sextans, and Ursa Minor have a feature similar to the barium-iron correlation
in Galactic metal-poor stars. The common feature of these two correlations can
be realized by our inhomogeneous chemical evolution model based on the
supernova-driven star formation scenario if dSph stars formed from gas with a
velocity dispersion of ~26 km/s. This velocity dispersion together with the
stellar luminosities strongly suggest that dark matter dominated dSph galaxies.
The tidal force of the Milky Way links this velocity dispersion with the
currently observed value <10 km/s by stripping the dark matter in dSph
galaxies. As a result, the total mass of each dSph galaxy is found to have been
originally ~25 times larger than at present. Our inhomogeneous chemical
evolution model succeeds in reproducing the stellar [Fe/H] distribution
function observed in Sextans. In this model, supernovae immediately after the
end of the star formation epoch can expel the remaining gas over the
gravitational potential of the dSph galaxy.
