def compute_actions_offset(self,
pos_offset,
vel_offset,
cadence=10,
end=1000):
orbit = self.mw.integrate_orbit(self.q,
dt=self.dt,
t1=self.t1,
t2=self.t2)
pos = np.transpose(orbit.pos.xyz)
pos = np.add(pos, pos_offset)
vel = np.transpose(orbit.vel.d_xyz)
vel = np.add(vel, vel_offset)
pos = np.transpose(pos)
vel = np.transpose(vel)
all_q = gd.PhaseSpacePosition(pos=pos, vel=vel)
out = []
time = orbit.t
with warnings.catch_warnings(record=True):
for q, t in tqdm(zip(all_q[0:end:cadence], time[0:end:cadence])):
try:
orbit = self.mw.integrate_orbit(q,
dt=self.dt,
t1=self.t1,
t2=self.t2)
res = gd.find_actions(orbit, N_max=self.N_max)
res['time'] = t
out.append(res)
except:
np.nan
return out
def __init__(self,
init_pos,
init_vel,
mw=None,
t1=0 * u.Gyr,
t2=5 * u.Gyr,
dt=1 * u.Myr,
N_max=8,
save_orbit=False):
if mw is None:
self.mw = gp.MilkyWayPotential()
else:
self.mw = mw
self.t1 = t1
self.t2 = t2
self.dt = dt
self.N_max = 8
self.q = gd.PhaseSpacePosition(pos=init_pos, vel=init_vel)
with warnings.catch_warnings(record=True):
warnings.simplefilter("ignore")
orbit = self.mw.integrate_orbit(self.q,
dt=self.dt,
t1=self.t1,
t2=self.t2)
self.res = gd.find_actions(orbit, N_max=self.N_max)
self.zmax = orbit.zmax()
if save_orbit:
#optional since orbit breaks pickling
self.orbit = orbit
def calculate_actions(w0,
pot=gp.MilkyWayPotential(),
dt=0.5,
n_steps=10000,
full_output=False):
""" Approximate actions following https://github.com/adrn/gala/blob/master/docs/dynamics/actionangle.rst """
assert len(w0.shape) == 0
w = gp.Hamiltonian(pot).integrate_orbit(w0, dt=dt, n_steps=n_steps)
toy_potential = gd.fit_isochrone(w)
toy_actions, toy_angles, toy_freqs = toy_potential.action_angle(w)
with warnings.catch_warnings(record=True):
warnings.simplefilter("ignore")
result = gd.find_actions(w, N_max=8, toy_potential=toy_potential)
if full_output: return result, w
return result["actions"]
agama.setUnits(mass=1, length=1, velocity=1)
# import the MW potential from gala
bulge = agama.Potential(type='Dehnen', gamma=1, mass=5E9, scaleRadius=1.0)
nucleus = agama.Potential(type='Dehnen',
gamma=1,
mass=1.71E09,
scaleRadius=0.07)
disk = agama.Potential(type='MiyamotoNagai',
mass=6.80e+10,
scaleRadius=3.0,
scaleHeight=0.28)
halo = agama.Potential(type='NFW', mass=5.4E11, scaleRadius=15.62)
mwpot = agama.Potential(bulge, nucleus, disk, halo)
af = agama.ActionFinder(mwpot, interp=False)
pos_vel = np.array([8., 0., 0., 75., 150., 50.])
agama_act = af(pos_vel)
# now do it for gala
pot = gp.MilkyWayPotential()
w0 = gd.PhaseSpacePosition(pos=[8, 0, 0.] * u.kpc,
vel=[75, 150, 50.] * u.km / u.s)
w = gp.Hamiltonian(pot).integrate_orbit(w0, dt=0.5, n_steps=10000)
gala_act = gd.find_actions(w, N_max=8)