Cos(m phi) disk potential

Generalization of the lopsided and elliptical disk potentials to any m.

class galpy.potential.CosmphiDiskPotential(amp=1.0, phib=0.4363323129985824, p=1.0, phio=0.01, m=1.0, r1=1.0, tform=None, tsteady=None, cp=None, sp=None, ro=None, vo=None)

Class that implements the disk potential

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

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, phio=0.01, m=1.0, r1=1.0, tform=None, tsteady=None, cp=None, sp=None, ro=None, vo=None)

NAME:

__init__

PURPOSE:

initialize an cosmphi disk potential

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

INPUT:

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

m= cos( m * (phi - phib) )

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)

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

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

OUTPUT:

(none)

HISTORY:

2011-10-27 - Started - Bovy (IAS)