# Source code for galpy.potential.TwoPowerTriaxialPotential

###############################################################################
#   TwoPowerTriaxialPotential.py: General class for triaxial potentials
#                                 derived from densities with two power-laws
#
#                                                    amp/[4pia^3]
#                             rho(r)= ------------------------------------
#                                      (m/a)^\alpha (1+m/a)^(\beta-\alpha)
#
#                             with
#
#                             m^2 = x^2 + y^2/b^2 + z^2/c^2
###############################################################################
import numpy
from scipy import special
from ..util import conversion
from .EllipsoidalPotential import EllipsoidalPotential
[docs]class TwoPowerTriaxialPotential(EllipsoidalPotential):
"""Class that implements triaxial potentials that are derived from
two-power density models

.. math::

\\rho(x,y,z) = \\frac{\\mathrm{amp}}{4\\,\\pi\\,a^3}\\,\\frac{1}{(m/a)^\\alpha\\,(1+m/a)^{\\beta-\\alpha}}

with

.. math::

m^2 = x'^2 + \\frac{y'^2}{b^2}+\\frac{z'^2}{c^2}

and :math:(x',y',z') is a rotated frame wrt :math:(x,y,z) specified by parameters zvec and pa which specify (a) zvec: the location of the :math:z' axis in the :math:(x,y,z) frame and (b) pa: the position angle of the :math:x' axis wrt the :math:\\tilde{x} axis, that is, the :math:x axis after rotating to zvec.

Note that this general class of potentials does *not* automatically revert to the special TriaxialNFWPotential, TriaxialHernquistPotential, or TriaxialJaffePotential when using their (alpha,beta) values (like TwoPowerSphericalPotential).
"""
[docs]    def __init__(self,amp=1.,a=5.,alpha=1.5,beta=3.5,b=1.,c=1.,
zvec=None,pa=None,glorder=50,
normalize=False,ro=None,vo=None):
"""
NAME:

__init__

PURPOSE:

initialize a triaxial two-power-density potential

INPUT:

amp - amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass or Gxmass

a - scale radius (can be Quantity)

alpha - inner power (0 <= alpha < 3)

beta - outer power ( beta > 2)

b - y-to-x axis ratio of the density

c - z-to-x axis ratio of the density

zvec= (None) If set, a unit vector that corresponds to the z axis

pa= (None) If set, the position angle of the x axis (rad or Quantity)

glorder= (50) if set, compute the relevant force and potential integrals with Gaussian quadrature of this order

normalize - if True, normalize such that vc(1.,0.)=1., or, if given as a number, such that the force is this fraction of the force necessary to make vc(1.,0.)=1.

ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)

OUTPUT:

(none)

HISTORY:

2016-05-30 - Started - Bovy (UofT)

2018-08-07 - Re-written using the general EllipsoidalPotential class - Bovy (UofT)

"""
EllipsoidalPotential.__init__(self,amp=amp,b=b,c=c,
zvec=zvec,pa=pa,glorder=glorder,
ro=ro,vo=vo,amp_units='mass')
a= conversion.parse_length(a,ro=self._ro)
self.a= a
self._scale= self.a
if beta <= 2. or alpha >= 3.:
raise IOError('TwoPowerTriaxialPotential requires 0 <= alpha < 3 and beta > 2')
self.alpha= alpha
self.beta= beta
self.betaminusalpha= self.beta-self.alpha
self.twominusalpha= 2.-self.alpha
self.threeminusalpha= 3.-self.alpha
if self.twominusalpha != 0.:
self.psi_inf= special.gamma(self.beta-2.)\
*special.gamma(3.-self.alpha)\
/special.gamma(self.betaminusalpha)
# Adjust amp
self._amp/= (4.*numpy.pi*self.a**3)
if normalize or \
(isinstance(normalize,(int,float)) \
and not isinstance(normalize,bool)): #pragma: no cover
self.normalize(normalize)
return None

def _psi(self,m):
"""\psi(m) = -\int_m^\infty d m^2 \rho(m^2)"""
if self.twominusalpha == 0.:
return -2.*self.a**2*(self.a/m)**self.betaminusalpha\
/self.betaminusalpha\
*special.hyp2f1(self.betaminusalpha,
self.betaminusalpha,
self.betaminusalpha+1,
-self.a/m)
else:
return -2.*self.a**2\
*(self.psi_inf-(m/self.a)**self.twominusalpha\
/self.twominusalpha\
*special.hyp2f1(self.twominusalpha,
self.betaminusalpha,
self.threeminusalpha,
-m/self.a))

def _mdens(self,m):
"""Density as a function of m"""
return (self.a/m)**self.alpha/(1.+m/self.a)**(self.betaminusalpha)

def _mdens_deriv(self,m):
"""Derivative of the density as a function of m"""
return -self._mdens(m)*(self.a*self.alpha+self.beta*m)/m/(self.a+m)

def _mass(self,R,z=None,t=0.):
"""
NAME:
_mass
PURPOSE:
evaluate the mass within R (and z) for this potential; if z=None, integrate to ellipsoidal boundary
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
t - time
OUTPUT:
the mass enclosed
HISTORY:
2021-03-09 - Written - Bovy (UofT)
"""
if not z is None: raise AttributeError # Hack to fall back to general
return 4.*numpy.pi*self.a**self.alpha\
*R**(3.-self.alpha)/(3.-self.alpha)*self._b*self._c\
*special.hyp2f1(3.-self.alpha,self.betaminusalpha,
4.-self.alpha,-R/self.a)

[docs]class TriaxialHernquistPotential(EllipsoidalPotential):
"""Class that implements the triaxial Hernquist potential

.. math::

\\rho(x,y,z) = \\frac{\\mathrm{amp}}{4\\,\\pi\\,a^3}\\,\\frac{1}{(m/a)\\,(1+m/a)^{3}}

with

.. math::

m^2 = x'^2 + \\frac{y'^2}{b^2}+\\frac{z'^2}{c^2}

and :math:(x',y',z') is a rotated frame wrt :math:(x,y,z) specified by parameters zvec and pa which specify (a) zvec: the location of the :math:z' axis in the :math:(x,y,z) frame and (b) pa: the position angle of the :math:x' axis wrt the :math:\\tilde{x} axis, that is, the :math:x axis after rotating to zvec.

"""
[docs]    def __init__(self,amp=1.,a=2.,normalize=False,b=1.,c=1.,zvec=None,pa=None,
glorder=50,ro=None,vo=None):
"""
NAME:

__init__

PURPOSE:

Initialize a triaxial Hernquist potential

INPUT:

amp - amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass or Gxmass

a - scale radius (can be Quantity)

b - y-to-x axis ratio of the density

c - z-to-x axis ratio of the density

zvec= (None) If set, a unit vector that corresponds to the z axis

pa= (None) If set, the position angle of the x axis

glorder= (50) if set, compute the relevant force and potential integrals with Gaussian quadrature of this order

normalize - if True, normalize such that vc(1.,0.)=1., or, if given as a number, such that the force is this fraction of the force necessary to make vc(1.,0.)=1.

ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)

OUTPUT:

(none)

HISTORY:

2010-07-09 - Written - Bovy (UofT)

2018-08-07 - Re-written using the general EllipsoidalPotential class - Bovy (UofT)

"""
EllipsoidalPotential.__init__(self,amp=amp,b=b,c=c,
zvec=zvec,pa=pa,glorder=glorder,
ro=ro,vo=vo,amp_units='mass')
a= conversion.parse_length(a,ro=self._ro)
self.a= a
self._scale= self.a
# Adjust amp
self.a4= self.a**4
self._amp/= (4.*numpy.pi*self.a**3)
if normalize or \
(isinstance(normalize,(int,float)) \
and not isinstance(normalize,bool)):
self.normalize(normalize)
self.hasC= not self._glorder is None
self.hasC_dxdv= False
self.hasC_dens= self.hasC # works if mdens is defined, necessary for hasC
return None

def _psi(self,m):
"""\psi(m) = -\int_m^\infty d m^2 \rho(m^2)"""
return -self.a4/(m+self.a)**2.

def _mdens(self,m):
"""Density as a function of m"""
return self.a4/m/(m+self.a)**3

def _mdens_deriv(self,m):
"""Derivative of the density as a function of m"""
return -self.a4*(self.a+4.*m)/m**2/(self.a+m)**4

def _mass(self,R,z=None,t=0.):
"""
NAME:
_mass
PURPOSE:
evaluate the mass within R (and z) for this potential; if z=None, integrate to ellipsoidal boundary
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
t - time
OUTPUT:
the mass enclosed
HISTORY:
2021-03-16 - Written - Bovy (UofT)
"""
if not z is None: raise AttributeError # Hack to fall back to general
return 4.*numpy.pi*self.a4/self.a/(1.+self.a/R)**2./2.*self._b*self._c

[docs]class TriaxialJaffePotential(EllipsoidalPotential):
"""Class that implements the Jaffe potential

.. math::

\\rho(x,y,z) = \\frac{\\mathrm{amp}}{4\\,\\pi\\,a^3}\\,\\frac{1}{(m/a)^2\\,(1+m/a)^{2}}

with

.. math::

m^2 = x'^2 + \\frac{y'^2}{b^2}+\\frac{z'^2}{c^2}

and :math:(x',y',z') is a rotated frame wrt :math:(x,y,z) specified by parameters zvec and pa which specify (a) zvec: the location of the :math:z' axis in the :math:(x,y,z) frame and (b) pa: the position angle of the :math:x' axis wrt the :math:\\tilde{x} axis, that is, the :math:x axis after rotating to zvec.

"""
[docs]    def __init__(self,amp=1.,a=2.,b=1.,c=1.,zvec=None,pa=None,normalize=False,
glorder=50,ro=None,vo=None):
"""
NAME:

__init__

PURPOSE:

Initialize a Jaffe potential

INPUT:

amp - amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass or Gxmass

a - scale radius (can be Quantity)

b - y-to-x axis ratio of the density

c - z-to-x axis ratio of the density

zvec= (None) If set, a unit vector that corresponds to the z axis

pa= (None) If set, the position angle of the x axis

glorder= (50) if set, compute the relevant force and potential integrals with Gaussian quadrature of this order

normalize - if True, normalize such that vc(1.,0.)=1., or, if given as a number, such that the force is this fraction of the force necessary to make vc(1.,0.)=1.

ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)

OUTPUT:

(none)

HISTORY:

2010-07-09 - Written - Bovy (UofT)

2018-08-07 - Re-written using the general EllipsoidalPotential class - Bovy (UofT)

"""
EllipsoidalPotential.__init__(self,amp=amp,b=b,c=c,
zvec=zvec,pa=pa,glorder=glorder,
ro=ro,vo=vo,amp_units='mass')
a= conversion.parse_length(a,ro=self._ro)
self.a= a
self._scale= self.a
# Adjust amp
self.a2= self.a**2
self._amp/= (4.*numpy.pi*self.a2*self.a)
if normalize or \
(isinstance(normalize,(int,float)) \
and not isinstance(normalize,bool)): #pragma: no cover
self.normalize(normalize)
self.hasC= not self._glorder is None
self.hasC_dxdv= False
self.hasC_dens= self.hasC # works if mdens is defined, necessary for hasC
return None

def _psi(self,m):
"""\psi(m) = -\int_m^\infty d m^2 \rho(m^2)"""
return 2.*self.a2*(1./(1.+m/self.a)+numpy.log(1./(1.+self.a/m)))

def _mdens(self,m):
"""Density as a function of m"""
return self.a2/m**2/(1.+m/self.a)**2

def _mdens_deriv(self,m):
"""Derivative of the density as a function of m"""
return -2.*self.a2**2*(self.a+2.*m)/m**3/(self.a+m)**3

def _mass(self,R,z=None,t=0.):
"""
NAME:
_mass
PURPOSE:
evaluate the mass within R (and z) for this potential; if z=None, integrate to ellipsoidal boundary
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
t - time
OUTPUT:
the mass enclosed
HISTORY:
2021-03-16 - Written - Bovy (UofT)
"""
if not z is None: raise AttributeError # Hack to fall back to general
return 4.*numpy.pi*self.a*self.a2/(1.+self.a/R)*self._b*self._c

[docs]class TriaxialNFWPotential(EllipsoidalPotential):
"""Class that implements the triaxial NFW potential

.. math::

\\rho(x,y,z) = \\frac{\\mathrm{amp}}{4\\,\\pi\\,a^3}\\,\\frac{1}{(m/a)\\,(1+m/a)^{2}}

with

.. math::

m^2 = x'^2 + \\frac{y'^2}{b^2}+\\frac{z'^2}{c^2}

and :math:(x',y',z') is a rotated frame wrt :math:(x,y,z) specified by parameters zvec and pa which specify (a) zvec: the location of the :math:z' axis in the :math:(x,y,z) frame and (b) pa: the position angle of the :math:x' axis wrt the :math:\\tilde{x} axis, that is, the :math:x axis after rotating to zvec.

"""
[docs]    def __init__(self,amp=1.,a=2.,b=1.,c=1.,zvec=None,pa=None,
normalize=False,
conc=None,mvir=None,
glorder=50,vo=None,ro=None,
H=70.,Om=0.3,overdens=200.,wrtcrit=False):
"""
NAME:

__init__

PURPOSE:

Initialize a triaxial NFW potential

INPUT:

amp - amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass or Gxmass

a - scale radius (can be Quantity)

b - y-to-x axis ratio of the density

c - z-to-x axis ratio of the density

zvec= (None) If set, a unit vector that corresponds to the z axis

pa= (None) If set, the position angle of the x axis

glorder= (50) if set, compute the relevant force and potential integrals with Gaussian quadrature of this order

normalize - if True, normalize such that vc(1.,0.)=1., or, if given as a number, such that the force is this fraction of the force necessary to make vc(1.,0.)=1.

Alternatively, NFW potentials can be initialized using

conc= concentration

mvir= virial mass in 10^12 Msolar

in which case you also need to supply the following keywords

H= (default: 70) Hubble constant in km/s/Mpc

Om= (default: 0.3) Omega matter

overdens= (200) overdensity which defines the virial radius

wrtcrit= (False) if True, the overdensity is wrt the critical density rather than the mean matter density

ro=, vo= distance and velocity scales for translation into internal units (default from configuration file)

OUTPUT:

(none)

HISTORY:

2016-05-30 - Written - Bovy (UofT)

2018-08-06 - Re-written using the general EllipsoidalPotential class - Bovy (UofT)

"""
EllipsoidalPotential.__init__(self,amp=amp,b=b,c=c,
zvec=zvec,pa=pa,glorder=glorder,
ro=ro,vo=vo,amp_units='mass')
a= conversion.parse_length(a,ro=self._ro)
if conc is None:
self.a= a
else:
from ..potential import NFWPotential
dum= NFWPotential(mvir=mvir,conc=conc,ro=self._ro,vo=self._vo,
H=H,Om=Om,wrtcrit=wrtcrit,overdens=overdens)
self.a= dum.a
self._amp= dum._amp
self._scale= self.a
self.hasC= not self._glorder is None
self.hasC_dxdv= False
self.hasC_dens= self.hasC # works if mdens is defined, necessary for hasC
# Adjust amp
self.a3= self.a**3
self._amp/= (4.*numpy.pi*self.a3)
if normalize or \
(isinstance(normalize,(int,float)) \
and not isinstance(normalize,bool)):
self.normalize(normalize)
return None

def _psi(self,m):
"""\psi(m) = -\int_m^\infty d m^2 \rho(m^2)"""
return -2.*self.a3/(self.a+m)

def _mdens(self,m):
"""Density as a function of m"""
return self.a/m/(1.+m/self.a)**2

def _mdens_deriv(self,m):
"""Derivative of the density as a function of m"""
return -self.a3*(self.a+3.*m)/m**2/(self.a+m)**3

def _mass(self,R,z=None,t=0.):
"""
NAME:
_mass
PURPOSE:
evaluate the mass within R (and z) for this potential; if z=None, integrate to ellipsoidal boundary
INPUT:
R - Galactocentric cylindrical radius
z - vertical height
t - time
OUTPUT:
the mass enclosed
HISTORY:
2021-03-16 - Written - Bovy (UofT)
"""
if not z is None: raise AttributeError # Hack to fall back to general
return 4.*numpy.pi*self.a3*self._b*self._c\
*(numpy.log(1+R/self.a)-R/self.a/(1.+R/self.a))