Steady-state logarithmic spiral potential¶
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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)¶ 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 \(T_{\mathrm{steady}}\).
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__init__
(amp=1.0, omegas=0.65, A=-0.035, alpha=-7.0, m=2, gamma=0.7853981633974483, p=None, tform=None, tsteady=None)¶ NAME:
__init__PURPOSE:
initialize a logarithmic spiral potentialINPUT:
amp - amplitude to be applied to the potential (default: 1., A below)
gamma - angle between sun-GC line and the line connecting the peak of the spiral pattern at the Solar radius (in rad; default=45 degree)
A - force amplitude (alpha*potential-amplitude; default=0.035)
omegas= - pattern speed (default=0.65)
m= number of arms
Either provide:
- alpha=
- p= pitch angle (rad)
tform - start of spiral growth / spiral period (default: -Infinity)
tsteady - time from tform at which the spiral is fully grown / spiral period (default: 2 periods)
OUTPUT:
(none)HISTORY:
2011-03-27 - Started - Bovy (NYU)
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