def vesc(Pot,R):
"""
NAME:
vesc
PURPOSE:
calculate the escape velocity at R for potential Pot
INPUT:
Pot - Potential instances or list thereof
R - Galactocentric radius (can be Quantity)
OUTPUT:
escape velocity
HISTORY:
2011-10-09 - Written - Bovy (IAS)
"""
from galpy.potential import evaluateplanarPotentials
from galpy.potential import PotentialError
try:
return nu.sqrt(2.*(evaluateplanarPotentials(Pot,_INF,use_physical=False)-evaluateplanarPotentials(Pot,R,use_physical=False)))
except PotentialError:
from galpy.potential import RZToplanarPotential
Pot= RZToplanarPotential(Pot)
return nu.sqrt(2.*(evaluateplanarPotentials(Pot,_INF,use_physical=False)-evaluateplanarPotentials(Pot,R,use_physical=False)))
def vcirc(Pot, R):
"""
NAME:
vcirc
PURPOSE:
calculate the circular velocity at R in potential Pot
INPUT:
Pot - Potential instance or list of such instances
R - Galactocentric radius
OUTPUT:
circular rotation velocity
HISTORY:
2011-10-09 - Written - Bovy (IAS)
"""
from galpy.potential import evaluateplanarRforces
from galpy.potential import PotentialError
try:
return nu.sqrt(-R * evaluateplanarRforces(R, Pot))
except PotentialError:
from galpy.potential import RZToplanarPotential
Pot = RZToplanarPotential(Pot)
return nu.sqrt(-R * evaluateplanarRforces(R, Pot))
def dvcircdR(Pot, R, phi=None):
"""
NAME:
dvcircdR
PURPOSE:
calculate the derivative of the circular velocity wrt R at R in potential Pot
INPUT:
Pot - Potential instance or list of such instances
R - Galactocentric radius (can be Quantity)
phi= (None) azimuth to use for non-axisymmetric potentials
OUTPUT:
derivative of the circular rotation velocity wrt R
HISTORY:
2013-01-08 - Written - Bovy (IAS)
2016-06-28 - Added phi= keyword for non-axisymmetric potential - Bovy (UofT)
"""
from galpy.potential import evaluateplanarRforces, evaluateplanarR2derivs
from galpy.potential import PotentialError
tvc = vcirc(Pot, R, phi=phi, use_physical=False)
try:
return 0.5 * (
-evaluateplanarRforces(Pot, R, phi=phi, use_physical=False) + R *
evaluateplanarR2derivs(Pot, R, phi=phi, use_physical=False)) / tvc
except PotentialError:
from galpy.potential import RZToplanarPotential
Pot = RZToplanarPotential(Pot)
return 0.5 * (
-evaluateplanarRforces(Pot, R, phi=phi, use_physical=False) + R *
evaluateplanarR2derivs(Pot, R, phi=phi, use_physical=False)) / tvc
def calcEscapecurve(Pot, Rs):
"""
NAME:
calcEscapecurve
PURPOSE:
calculate the escape velocity curve for this potential (in the
z=0 plane for non-spherical potentials)
INPUT:
Pot - Potential or list of Potential instances
Rs - (array of) radius(i)
OUTPUT:
array of v_esc
HISTORY:
2011-04-16 - Written - Bovy (NYU)
"""
isList = isinstance(Pot, list)
isNonAxi = ((isList and Pot[0].isNonAxi) or (not isList and Pot.isNonAxi))
if isNonAxi:
raise AttributeError(
"Escape velocity curve plotting for non-axisymmetric potentials is not currently supported"
)
try:
grid = len(Rs)
except TypeError:
grid = 1
Rs = nu.array([Rs])
esccurve = nu.zeros(grid)
from galpy.potential import evaluateplanarPotentials
from galpy.potential import PotentialError
for ii in range(grid):
try:
esccurve[ii] = nu.sqrt(2. *
(evaluateplanarPotentials(_INF, Pot) -
evaluateplanarPotentials(Rs[ii], Pot)))
except PotentialError:
from galpy.potential import RZToplanarPotential
Pot = RZToplanarPotential(Pot)
esccurve[ii] = nu.sqrt(2. *
(evaluateplanarPotentials(_INF, Pot) -
evaluateplanarPotentials(Rs[ii], Pot)))
return esccurve
def dvcircdR(Pot, R):
"""
NAME:
dvcircdR
PURPOSE:
calculate the derivative of the circular velocity wrt R at R in potential Pot
INPUT:
Pot - Potential instance or list of such instances
R - Galactocentric radius
OUTPUT:
derivative of the circular rotation velocity wrt R
HISTORY:
2013-01-08 - Written - Bovy (IAS)
"""
from galpy.potential import evaluateplanarRforces, evaluateplanarR2derivs
from galpy.potential import PotentialError
tvc = vcirc(Pot, R)
try:
return 0.5 * (-evaluateplanarRforces(R, Pot) +
R * evaluateplanarR2derivs(R, Pot)) / tvc
except PotentialError:
from galpy.potential import RZToplanarPotential
Pot = RZToplanarPotential(Pot)
return 0.5 * (-evaluateplanarRforces(R, Pot) +
R * evaluateplanarR2derivs(R, Pot)) / tvc