  We investigate a simple model for a galactic halo under the assumption that
it is dominated by a dark matter component in the form of a Bose-Einstein
condensate involving an ultra-light scalar particle. In particular we discuss
the possibility if the dark matter is in superfluid state then a rotating
galactic halo might contain quantised vortices which would be low-energy
analogues of cosmic strings. Using known solutions for the density profiles of
such vortices we compute the self-gravitational interactions in such halos and
place bounds on the parameters describing such models, such as the mass of the
particles involved.
