We report analytical and numerical results for the critical velocity for
dissipationless motion of a two-dimensional scalar superfluid past a localized
and static repulsive obstacle. In contrast to most of the state of the art, our
study is not restricted to an impenetrable obstacle, nor to a quartic
interaction. This makes it possible to get closer to recent experiments with
atomic Bose-Einstein condensates and paraxial superfluids of light.Comment: 9 pages, 2 figure