# Three Miyamoto-Nagai disk approximation to an exponential disk¶

class galpy.potential.MN3ExponentialDiskPotential(amp=1.0, hr=0.3333333333333333, hz=0.0625, sech=False, posdens=False, normalize=False, ro=None, vo=None)[source]

class that implements the three Miyamoto-Nagai approximation to a radially-exponential disk potential of Smith et al. 2015

$\rho(R,z) = \mathrm{amp}\,\exp\left(-R/h_R-|z|/h_z\right)$

or

$\rho(R,z) = \mathrm{amp}\,\exp\left(-R/h_R\right)\mathrm{sech}^2\left(-|z|/h_z\right)$

depending on whether sech=True or not. This density is approximated using three Miyamoto-Nagai disks

__init__(amp=1.0, hr=0.3333333333333333, hz=0.0625, sech=False, posdens=False, normalize=False, ro=None, vo=None)[source]

NAME:

__init__

PURPOSE:

initialize a 3MN approximation to an exponential disk potential

INPUT:

amp - amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass density or Gxmass density

hr - disk scale-length (can be Quantity)

hz - scale-height (can be Quantity)

sech= (False) if True, hz is the scale height of a sech vertical profile (default is exponential vertical profile)

posdens= (False) if True, allow only positive density solutions (Table 2 in Smith et al. rather than Table 1)

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.

ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)

OUTPUT:

MN3ExponentialDiskPotential object

HISTORY:

2015-02-07 - Written - Bovy (IAS)