Simple and accurate modelling of the gravitational potential produced by
  thick and thin exponential disks
  We present accurate models of the gravitational potential produced by a
radially exponential disk mass distribution. The models are produced by
combining three separate Miyamoto-Nagai disks. Such models have been used
previously to model the disk of the Milky Way, but here we extend this
framework to allow its application to disks of any mass, scalelength, and a
wide range of thickness from infinitely thin to near spherical (ellipticities
from 0 to 0.9). The models have the advantage of simplicity of implementation,
and we expect faster run speeds over a double exponential disk treatment. The
potentials are fully analytical, and differentiable at all points. The mass
distribution of our models deviates from the radial mass distribution of a pure
exponential disk by <0.4% out to 4 disk scalelengths, and <1.9% out to 10 disk
scalelengths. We tabulate fitting parameters which facilitate construction of
exponential disks for any scalelength, and a wide range of disk thickness (a
user-friendly, web-based interface is also available). Our recipe is well
suited for numerical modelling of the tidal effects of a giant disk galaxy on
star clusters or dwarf galaxies. We consider three worked examples; the Milky
Way thin and thick disk, and a disky dwarf galaxy.
