Steady-state logarithmic spiral potential

class galpy.potential.SteadyLogSpiralPotential(amp=1.0, omegas=0.65, A=-0.035, alpha=-7.0, m=2, gamma=0.7853981633974483, p=None, tform=None, tsteady=None, ro=None, vo=None)

Class that implements a steady-state spiral potential

\[\Phi(R,\phi) = \frac{\mathrm{amp}\times A}{\alpha}\,\cos\left(\alpha\,\ln R - m\,(\phi-\Omega_s\,t-\gamma)\right)\]

Can be grown in a similar way as the DehnenBarPotential, but using \(T_s = 2\pi/\Omega_s\) to normalize \(t_{\mathrm{form}}\) and \(t_{\mathrm{steady}}\). If the pattern speed is zero, \(t_\mathrm{form}\) and \(t_\mathrm{steady}\) are straight times, not times divided by the spiral period.

__init__(amp=1.0, omegas=0.65, A=-0.035, alpha=-7.0, m=2, gamma=0.7853981633974483, p=None, tform=None, tsteady=None, ro=None, vo=None)

Initialize a steady-state logarithmic spiral potential.

Parameters:

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

• omegas (float or Quantity, optional) – Pattern speed (default: 0.65).

• A (float or Quantity, optional) – Amplitude (alpha*potential-amplitude; default=0.035).

• alpha (float, optional) – Parameter that sets the strength of the spiral potential.

• m (int, optional) – Number of spiral arms.

• gamma (float or Quantity, optional) – Angle between sun-GC line and the line connecting the peak of the spiral pattern at the Solar radius (in rad; default=45 degree).

• p (float or Quantity, optional) – Pitch angle.

• tform (float, optional) – Start of spiral growth / spiral period (default: -Infinity).

• tsteady (float, optional) – Time from tform at which the spiral is fully grown / spiral period (default: 2 periods).

• 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

• 2011-03-27 - Started - Bovy (NYU)