Source code for gala.coordinates.orphan

""" 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