Potential (galpy.potential)

3D potentials

General instance routines

Use as Potential-instance.method(...)

In addition to these, the NFWPotential also has methods to calculate virial quantities

Specific potentials

All of the following potentials can also be modified by the specific WrapperPotentials listed below.

General Poisson solvers for disks and halos

In addition to these classes, a simple Milky-Way-like potential fit to data on the Milky Way is included as galpy.potential.MWPotential2014 (see the galpy paper for details). Note that this potential assumes a circular velocity of 220 km/s at the solar radius at 8 kpc; see arXiv/1412.3451 for full information on how this potential was fit. This potential is defined as

>>> bp= PowerSphericalPotentialwCutoff(alpha=1.8,rc=1.9/8.,normalize=0.05)
>>> mp= MiyamotoNagaiPotential(a=3./8.,b=0.28/8.,normalize=.6)
>>> np= NFWPotential(a=16/8.,normalize=.35)
>>> MWPotential2014= [bp,mp,np]

and can thus be used like any list of Potentials. If one wants to add the supermassive black hole at the Galactic center, this can be done by

>>> from galpy.potential import KeplerPotential
>>> from galpy.util import bovy_conversion
>>> MWPotential2014.append(KeplerPotential(amp=4*10**6./bovy_conversion.mass_in_msol(220.,8.)))

for a black hole with a mass of \(4\times10^6\,M_{\odot}\).

As explained in this section, without this black hole MWPotential2014 can be used with Dehnen’s gyrfalcON code using accname=PowSphwCut+MiyamotoNagai+NFW and accpars=0,1001.79126907,1.8,1.9#0,306770.418682,3.0,0.28#0,16.0,162.958241887.

An older version galpy.potential.MWPotential of a similar potential that was not fit to data on the Milky Way is defined as

>>> mp= MiyamotoNagaiPotential(a=0.5,b=0.0375,normalize=.6)
>>> np= NFWPotential(a=4.5,normalize=.35)
>>> hp= HernquistPotential(a=0.6/8,normalize=0.05)
>>> MWPotential= [mp,np,hp]

galpy.potential.MWPotential2014 supersedes galpy.potential.MWPotential.

2D potentials

General instance routines

Use as Potential-instance.method(...)

General axisymmetric potential instance routines

Use as Potential-instance.method(...)

Specific potentials

All of the 3D potentials above can be used as two-dimensional potentials in the mid-plane.

In addition, a two-dimensional bar potential, two spiral potentials, and some static non-axisymmetric perturbations are included

1D potentials

General instance routines

Use as Potential-instance.method(...)

Specific potentials

One-dimensional potentials can also be derived from 3D axisymmetric potentials as the vertical potential at a certain Galactocentric radius

Potential wrappers

Gravitational potentials in galpy can also be modified using wrappers, for example, to change their amplitude as a function of time. These wrappers can be applied to any galpy potential (although whether they can be used in C depends on whether the wrapper and all of the potentials that it wraps are implemented in C). Multiple wrappers can be applied to the same potential.