# Elliptical disk potential¶

Like in Kuijken & Tremaine. See galpy.potential.CosmphiDiskPotential for a more general version that allows for a break radius within which the radial dependence of the potential changes from R^p to R^-p (elliptical disk corresponds to m=2).

class galpy.potential.EllipticalDiskPotential(amp=1.0, phib=0.4363323129985824, p=1.0, twophio=0.01, r1=1.0, tform=None, tsteady=None, cp=None, sp=None, ro=None, vo=None)[source]

Class that implements the Elliptical disk potential of Kuijken & Tremaine (1994)

$\Phi(R,\phi) = \mathrm{amp}\,\phi_0\,\left(\frac{R}{R_1}\right)^p\,\cos\left(2\,(\phi-\phi_b)\right)$

This potential can be grown between $$t_{\mathrm{form}}$$ and $$t_{\mathrm{form}}+T_{\mathrm{steady}}$$ in a similar way as DehnenBarPotential, but times are given directly in galpy time units

__init__(amp=1.0, phib=0.4363323129985824, p=1.0, twophio=0.01, r1=1.0, tform=None, tsteady=None, cp=None, sp=None, ro=None, vo=None)[source]

Initialize an Elliptical disk potential.

Parameters:
• amp (float, optional) – Amplitude to be applied to the potential (default: 1.), see twophio below.

• tform (float or Quantity, optional) – Start of growth (to smoothly grow this potential).

• tsteady (float or Quantity, optional) – Time delay at which the perturbation is fully grown (default: 2.).

• p (float, optional) – Power-law index of the phi(R) = (R/Ro)^p part.

• r1 (float or Quantity, optional) – Normalization radius for the amplitude.

• phib (float or Quantity, optional) – Angle (in rad; default=25 degree).

• twophio (float or Quantity, optional) – Potential perturbation (in terms of 2phio/vo^2 if vo=1 at Ro=1).

• cp (float or Quantity, optional) – Twophio * cos(2phib).

• sp (float or Quantity, optional) – Twophio * sin(2phib).

• ro (float or Quantity, optional) – Distance scale for translation into internal units (default from configuration file).

• vo (float or Quantity, optional) – Velocity scale for translation into internal units (default from configuration file).

Notes

• Specify either (phib,twophio) or (cp,sp).

• 2011-10-19 - Started - Bovy (IAS)