  As is usual in dwarf spheroidal galaxies, today the Local Group galaxy Ursa
Minor is depleted of its gas content. How this galaxy lost its gas is still a
matter of debate. To study the history of gas loss in Ursa Minor, we conducted
the first three-dimensional hydrodynamical simulations of this object, assuming
that the gas loss was driven by galactic winds powered only by type II
supernovae (SNe II). The initial gas setup and supernova (SN) rates used in our
simulations are mainly constrained by the inferred star formation history and
the observed velocity dispersion of Ursa Minor. After 3 Gyr of evolution, we
found that the gas removal efficiency is higher when the SN rate is increased,
and also when the initial mean gas density is lowered. The derived mass-loss
rates are systematically higher in the central regions (<300 pc), even though
such a relationship has not been strictly linear in time and in terms of the
galactic radius. The filamentary structures induced by Rayleigh-Taylor
instabilities and the concentric shells related to the acoustic waves driven by
SNe can account for the inferred mass losses from the simulations. Our results
suggest that SNe II are able to transfer most of the gas from the central
region outward to the galactic halo. However, other physical mechanisms must be
considered in order to completely remove the gas at larger radii.
