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)