A very simple bar model for the Milky Way in galpy

SimpleBarModel.ipynb

Hi, you can add a SpiralArmsPotential, for example

SpiralArmsPotential(N=2,amp=0.75,phi_ref=25.*u.deg,alpha=15.*u.deg,omega=2./3.)

gives a two-armed spiral with a 15 degree pitch angle, a pattern speed of 2/3 Omega_sun (where Omega_sun is the rotational frequency at the Sun, Vc/R0), and it has an amplitude such that the spiral is a ~15% density enhancement at the Solar radius.

Note that the notebook above is quite old and will not work using the current version of galpy. I think the main necessary change is to replace

from galpy.util import bovy_coords, bovy_plot

with

from galpy.util import coords as bovy_coords, plot as bovy_plot

because those modules were renamed, but there might be other necessary changes.

Thank you very much !

Dear Bovy,
Does the amplitude you recommend take into account the conservation of the mass distribution?
Additionally, what happens if I change the number of spiral arms from 2 to 4?
Thank you!