# 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]

NAME:

__init__

PURPOSE:

initialize an Elliptical disk potential

phi(R,phi) = phio (R/Ro)^p cos[2(phi-phib)]

INPUT:

amp= amplitude to be applied to the potential (default: 1.), see twophio below

tform= start of growth (to smoothly grow this potential (can be Quantity)

tsteady= time delay at which the perturbation is fully grown (default: 2.; can be Quantity)

p= power-law index of the phi(R) = (R/Ro)^p part

r1= (1.) normalization radius for the amplitude (can be Quantity)

Either:

1. phib= angle (in rad; default=25 degree; or can be Quantity)

twophio= potential perturbation (in terms of 2phio/vo^2 if vo=1 at Ro=1; can be Quantity with units of velocity-squared)

2. cp, sp= twophio * cos(2phib), twophio * sin(2phib) (can be Quantity with units of velocity-squared)

OUTPUT:

(none)

HISTORY:

2011-10-19 - Started - Bovy (IAS)