""" Astropy coordinate class for the Magellanic Stream coordinate system """
from astropy.coordinates.matrix_utilities import (rotation_matrix,
matrix_product,
matrix_transpose)
from astropy.coordinates.baseframe import (frame_transform_graph,
BaseCoordinateFrame,
RepresentationMapping)
from astropy.coordinates.transformations import StaticMatrixTransform
from astropy.coordinates import representation as r
from astropy.coordinates import Galactic
import astropy.units as u
__all__ = ["MagellanicStreamNidever08", "MagellanicStream"]
[docs]class MagellanicStreamNidever08(BaseCoordinateFrame):
"""
A coordinate or frame aligned with the Magellanic Stream,
as defined by Nidever et al. (2008,
see: `<http://adsabs.harvard.edu/abs/2008ApJ...679..432N>`_).
For more information about this class, see the Astropy documentation
on coordinate frames in :mod:`~astropy.coordinates`.
Examples
--------
Converting the coordinates of the Large Magellanic Cloud:
>>> from astropy import coordinates as coord
>>> from astropy import units as u
>>> from gala.coordinates import MagellanicStreamNidever08
>>> c = coord.Galactic(l=280.4652*u.deg, b=-32.8884*u.deg)
>>> ms = c.transform_to(MagellanicStreamNidever08())
>>> print(ms)
<MagellanicStreamNidever08 Coordinate: (L, B) in deg
(-0.13686116, 2.42583948)>
"""
frame_specific_representation_info = {
r.SphericalRepresentation: [
RepresentationMapping('lon', 'L'),
RepresentationMapping('lat', 'B')
]
}
default_representation = r.SphericalRepresentation
default_differential = r.SphericalCosLatDifferential
_ngp = Galactic(l=188.5*u.deg, b=-7.5*u.deg)
_lon0 = Galactic(l=280.47*u.deg, b=-32.75*u.deg)
_default_wrap_angle = 180*u.deg
def __init__(self, *args, **kwargs):
wrap = kwargs.pop('wrap_longitude', True)
super().__init__(*args, **kwargs)
if wrap and isinstance(self._data, (r.UnitSphericalRepresentation,
r.SphericalRepresentation)):
self._data.lon.wrap_angle = self._default_wrap_angle
# TODO: remove this. This is a hack required as of astropy v3.1 in order
# to have the longitude components wrap at the desired angle
[docs] def represent_as(self, base, s='base', in_frame_units=False):
r = super().represent_as(base, s=s, in_frame_units=in_frame_units)
if hasattr(r, "lon"):
r.lon.wrap_angle = self._default_wrap_angle
return r
represent_as.__doc__ = BaseCoordinateFrame.represent_as.__doc__
@frame_transform_graph.transform(StaticMatrixTransform,
Galactic, MagellanicStreamNidever08)
def gal_to_mag():
mat1 = rotation_matrix(57.275785782128686*u.deg, 'z')
mat2 = rotation_matrix(90*u.deg - MagellanicStreamNidever08._ngp.b, 'y')
mat3 = rotation_matrix(MagellanicStreamNidever08._ngp.l, 'z')
return matrix_product(mat1, mat2, mat3)
@frame_transform_graph.transform(StaticMatrixTransform,
MagellanicStreamNidever08, Galactic)
def mag_to_gal():
return matrix_transpose(gal_to_mag())
# TODO: remove this in next version
class MagellanicStream(MagellanicStreamNidever08):
def __init__(self, *args, **kwargs):
import warnings
warnings.warn("This frame is deprecated. Use MagellanicStreamNidever08 "
"instead.", DeprecationWarning)
super().__init__(*args, **kwargs)
trans = frame_transform_graph.get_transform(MagellanicStreamNidever08,
Galactic).transforms[0]
frame_transform_graph.add_transform(MagellanicStream, Galactic, trans)
trans = frame_transform_graph.get_transform(Galactic,
MagellanicStreamNidever08).transforms[0]
frame_transform_graph.add_transform(Galactic, MagellanicStream, trans)