rotate_coord
This IDL facility provides a means to rotate a set of 3D position
vectors (and their Stokes parameters Q and U) between to astrophysical coordinate systems
or by an arbitrary rotation.
Location in HEALPix directory tree: src/idl/misc/rotate_coord.pro
FORMAT
QUALIFIERS
-
Invec
- input, array of size (n,3) : set of 3D position vectors
-
Outvec
- output, array of size (n,3) : rotated 3D vectors, with the same norms as the input vectors
-
Delta_Psi
- output, vector of size (n) containing the change in azimuth in Radians
resulting from the rotation
(measured with respect to the local meridian, from South to East),
so that for field of spin s the output Q',U' is related to the input Q,U via
with s=2 for polarization Stokes parameters
(for which the specific Stokes_Parameters is also available).
-
Euler_Matrix=
- input, array of size (3,3). Euler Matrix
describing the rotation to apply to vectors.
default:identity : no rotation.
Can not be used together with a change in coordinates.
-
Inco=
- input, character string (either 'Q' or 'C': equatorial,
'G': galactic or 'E': ecliptic) describing the input coordinate system
-
Outco=
- input, character string (see above) describing the output
coordinate system.
Can not be used together with Euler_Matrix
-
Stokes_Parameters=
- input and output, array of size (n, 2) :
values of the Q and U Stokes parameters on the sphere for each of
the input position vector. Q and U are defined wrt the local
meridian and parallel and are therefore transformed in a
non-trivial way in case of rotation
KEYWORDS
-
/free_norm
- if set
(and Stokes_Parameters and/or
Delta_Psi are present)
the input (and output) coordinate vectors are not assumed to be normalized to 1.
Using this option is therefore safer, but 20 to 30% slower.
(Note that 3D vectors produced by
ang2vec,
pix2vec_nest and
pix2vec_ring are properly normalized).
Ignored when Stokes_Parameters and
Delta_Psi are both absent.
-
/help
- if set, the documentation header is printed and the routine exits
DESCRIPTION
rotate_coord is a generalisation of the Astro library routine skyconv. It allows
a rotation of 3D position vectors between two standard astronomic coordinates
system but also an arbitrary active rotation described by its Euler Matrix.
It can also compute how the linear polarization Stokes parameters (Q and U,
expressed in local coordinates system)
of each input location are affected by the solid body rotation, or equivalently
it can output the corresponding change in azimuth.
RELATED ROUTINES
This section lists the routines related to rotate_coord
-
idl
- version 6.4 or more is necessary to run rotate_coord.
-
euler_matrix_new
- constructs the Euler Matrix for a set of
three angles and three axes of rotation
-
ang2vec, pix2vec_*
- can be used to generate the input 3D vectors
Version 3.82, 2022-07-28