cylindrical_to_cartesian¶
-
gala.coordinates.
cylindrical_to_cartesian
(pos, vel)[source]¶ Convert a velocity in Spherical coordinates to Cylindrical coordinates. This follows the naming convention used in
astropy.coordinates
: cylindrical coordinates consist of a radius, \(\rho\), an azimuthal angle, \(\phi\), in the range [0, 360] deg, and a z coordinate, \(z\).The components of the output velocity all have units of velocity, i.e., this is not used for transforming from a cartesian velocity to angular velocities, but rather the velocity vector components in Eq. 2 below.
\[\begin{split}\boldsymbol{v} &= v_x\boldsymbol{\hat{x}} + v_y\boldsymbol{\hat{y}} + v_z\boldsymbol{\hat{z}}\\\\ &= v_\rho\boldsymbol{\hat{\rho}} + v_\phi\boldsymbol{\hat{\phi}} + v_z\boldsymbol{\hat{z}}\\\\ &= \dot{\rho}\boldsymbol{\hat{\rho}} + \rho\dot{\phi}\boldsymbol{\hat{\phi}} + \dot{z}\boldsymbol{\hat{\theta}}\end{split}\]Parameters: pos :
Quantity
,BaseCoordinateFrame
,BaseRepresentation
Input position or positions as one of the allowed types. You may pass in a
Quantity
withdimensionless_unscaled
units if you are working in natural units.vel :
Quantity
Input velocity or velocities as one of the allowed types. You may pass in a
Quantity
withdimensionless_unscaled
units if you are working in natural units. axis=0 is assumed to be the dimensionality axis, e.g.,vx,vy,vz = vel
should work.Returns: vxyz :
Quantity
Array of Cartesian velocity components. Will have the same shape as the input velocity.