Class that implements the logarithmic halo potential Phi(r)
NAME:
__init__
PURPOSE:
initialize a Logarithmic Halo potential
INPUT:
amp - amplitude to be applied to the potential (default: 1)
core - core radius at which the logarithm is cut
q - potential flattening (z/q)**2.
normalize - if True, normalize such that vc(1.,0.)=1., or, if given as a number, such that the force is this fraction of the force necessary to make vc(1.,0.)=1.
OUTPUT:
(none)
HISTORY:
2010-04-02 - Started - Bovy (NYU)