# Corotating rotation wrapper potential¶

class galpy.potential.CorotatingRotationWrapperPotential(*args, **kwargs)[source]

Potential wrapper class that implements rotation with fixed R x pattern-speed around the z-axis. Can be used to make spiral structure that is everywhere co-rotating. The potential is rotated by replacing

$\phi \rightarrow \phi + \frac{V_p(R)}{R} \times \left(t-t_0\right) + \mathrm{pa}$

with $$V_p(R)$$ the circular velocity curve, $$t_0$$ a reference time—time at which the potential is unchanged by the wrapper—and $$\mathrm{pa}$$ the position angle at $$t=0$$. The circular velocity is parameterized as

$V_p(R) = V_{p,0}\,\left(\frac{R}{R_0}\right)^\beta\,.$
__init__(amp=1.0, pot=None, vpo=1.0, beta=0.0, to=0.0, pa=0.0, ro=None, vo=None)[source]

Initialize a CorotatingRotationWrapper Potential.

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

• pot (Potential instance or list thereof, optional) – This potential is made to rotate around the z axis by the wrapper.

• vpo (float or Quantity, optional) – Amplitude of the circular-velocity curve.

• beta (float, optional) – Power-law amplitude of the circular-velocity curve.

• to (float or Quantity, optional) – Reference time at which the potential == pot.

• pa (float or Quantity, optional) – The position angle.

• 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

• 2018-02-21 - Started - Bovy (UofT)