""" Astropy coordinate class for the Orphan stream coordinate systems """
import astropy.coordinates as coord
import astropy.units as u
from astropy.coordinates import frame_transform_graph
from astropy.coordinates.matrix_utilities import rotation_matrix
import numpy as np
__all__ = ["OrphanNewberg10", "OrphanKoposov19"]
[docs]
class OrphanNewberg10(coord.BaseCoordinateFrame):
"""
A Heliocentric spherical coordinate system defined by the orbit
of the Orphan stream, as described in
Newberg et al. 2010 (see: `<http://arxiv.org/abs/1001.0576>`_).
Note: to be consistent with other stream classes, we refer to the longitude
and latitude as ``phi1`` and ``phi2`` instead of ``Lambda`` and ``Beta``.
For more information about this class, see the Astropy documentation
on coordinate frames in :mod:`~astropy.coordinates`.
Parameters
----------
representation : :class:`~astropy.coordinates.BaseRepresentation` or None
A representation object or None to have no data (or use the other keywords)
phi1 : angle_like, optional, must be keyword
The longitude-like angle corresponding to Orphan's orbit.
phi2 : angle_like, optional, must be keyword
The latitude-like angle corresponding to Orphan's orbit.
distance : :class:`~astropy.units.Quantity`, optional, must be keyword
The Distance for this object along the line-of-sight.
pm_phi1_cosphi2 : :class:`~astropy.units.Quantity`, optional, must be keyword
The proper motion in the longitude-like direction corresponding to
the Orphan stream's orbit.
pm_phi2 : :class:`~astropy.units.Quantity`, optional, must be keyword
The proper motion in the latitude-like direction perpendicular to the
Orphan stream's orbit.
radial_velocity : :class:`~astropy.units.Quantity`, optional, must be keyword
The Distance for this object along the line-of-sight.
"""
default_representation = coord.SphericalRepresentation
default_differential = coord.SphericalCosLatDifferential
frame_specific_representation_info = {
coord.SphericalRepresentation: [
coord.RepresentationMapping("lon", "phi1"),
coord.RepresentationMapping("lat", "phi2"),
coord.RepresentationMapping("distance", "distance"),
]
}
_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,
(coord.UnitSphericalRepresentation, coord.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__ = coord.BaseCoordinateFrame.represent_as.__doc__
# Define the Euler angles
phi = 128.79 * u.degree
theta = 54.39 * u.degree
psi = 90.70 * u.degree
# Generate the rotation matrix using the x-convention (see Goldstein)
D = rotation_matrix(phi, "z")
C = rotation_matrix(theta, "x")
B = rotation_matrix(psi, "z")
R = B @ C @ D
@frame_transform_graph.transform(
coord.StaticMatrixTransform, coord.Galactic, OrphanNewberg10
)
def galactic_to_orp():
"""Compute the transformation from Galactic spherical to
heliocentric Orphan coordinates.
"""
return R
# Oph to Galactic coordinates
@frame_transform_graph.transform(
coord.StaticMatrixTransform, OrphanNewberg10, coord.Galactic
)
def orp_to_galactic():
"""Compute the transformation from heliocentric Orphan coordinates to
spherical Galactic.
"""
return galactic_to_orp().T
# ------------------------------------------------------------------------------
[docs]
class OrphanKoposov19(coord.BaseCoordinateFrame):
"""A coordinate frame for the Orphan stream defined by Sergey Koposov.
Parameters
----------
phi1 : `~astropy.units.Quantity`
Longitude component.
phi2 : `~astropy.units.Quantity`
Latitude component.
distance : `~astropy.units.Quantity`
Distance.
pm_phi1_cosphi2 : `~astropy.units.Quantity`
Proper motion in longitude.
pm_phi2 : `~astropy.units.Quantity`
Proper motion in latitude.
radial_velocity : `~astropy.units.Quantity`
Line-of-sight or radial velocity.
"""
default_representation = coord.SphericalRepresentation
default_differential = coord.SphericalCosLatDifferential
frame_specific_representation_info = {
coord.SphericalRepresentation: [
coord.RepresentationMapping("lon", "phi1"),
coord.RepresentationMapping("lat", "phi2"),
coord.RepresentationMapping("distance", "distance"),
]
}
_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,
(coord.UnitSphericalRepresentation, coord.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__ = coord.BaseCoordinateFrame.represent_as.__doc__
@frame_transform_graph.transform(
coord.StaticMatrixTransform, coord.ICRS, OrphanKoposov19
)
def icrs_to_orp19():
"""Compute the transformation from ICRS to
heliocentric Orphan coordinates.
"""
R = np.array(
[
[-0.44761231, -0.08785756, -0.88990128],
[-0.84246097, 0.37511331, 0.38671632],
[0.29983786, 0.92280606, -0.2419219],
]
)
return R
# Oph to Galactic coordinates
@frame_transform_graph.transform(
coord.StaticMatrixTransform, OrphanKoposov19, coord.ICRS
)
def orp19_to_icrs():
"""Compute the transformation from heliocentric Orphan coordinates to
spherical ICRS.
"""
return icrs_to_orp19().T
