  We study vortex solutions in a holographic model of Herzog, Hartnoll, and
Horowitz, with a vanishing external magnetic field on the boundary, as is
appropriate for vortices in a superfluid. We study relevant length scales
related to the vortices and how the charge density inside the core of the
vortex behaves as a function of temperature or chemical potential. We extract
the critical superfluid velocity from the vortex solutions, study how it
behaves as a function of the temperature, and compare it to earlier studies and
to the Landau criterion. We also comment on the possibility of a
Berezinskii-Kosterlitz-Thouless vortex confinement-deconfinement transition.
