# Triaxial NFW potential¶

class galpy.potential.TriaxialNFWPotential(amp=1.0, a=2.0, b=1.0, c=1.0, zvec=None, pa=None, normalize=False, conc=None, mvir=None, glorder=50, vo=None, ro=None, H=70.0, Om=0.3, overdens=200.0, wrtcrit=False)[source]

Class that implements the triaxial NFW potential

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

with

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

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

__init__(amp=1.0, a=2.0, b=1.0, c=1.0, zvec=None, pa=None, normalize=False, conc=None, mvir=None, glorder=50, vo=None, ro=None, H=70.0, Om=0.3, overdens=200.0, wrtcrit=False)[source]

Initialize a triaxial NFW potential

Parameters:
• amp (float or Quantity, optional) – Amplitude to be applied to the potential (default: 1); can be a Quantity with units of mass or Gxmass

• a (float or Quantity, optional) – Scale radius.

• b (float, optional) – y-to-x axis ratio of the density

• c (float, optional) – z-to-x axis ratio of the density

• zvec (numpy.ndarray, optional) – If set, a unit vector that corresponds to the z axis

• pa (float or Quantity, optional) – If set, the position angle of the x axis

• glorder (int, optional) – If set, compute the relevant force and potential integrals with Gaussian quadrature of this order

• normalize (bool or float, optional) – 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.

• conc (float, optional) – Concentration.

• mvir (float, optional) – Virial mass in 10^12 Msolar.

• H (float, optional) – Hubble constant in km/s/Mpc.

• Om (float, optional) – Omega matter.

• overdens (float, optional) – Overdensity which defines the virial radius.

• wrtcrit (bool, optional) – If True, the overdensity is wrt the critical density rather than the mean matter density.

• ro (float or Quantity, optional) – Distance scale for translation into internal units (default from configuration file).

• vo (float or Quantity, optional) – Velocity scale for translation into internal units (default from configuration file).

Notes

• Initialize with one of:
• a and amp or normalize

• mvir, conc, H, Om, wrtcrit, overdens.

• 2010-07-09 - Written - Bovy (UofT)

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