Source code for gala.coordinates.pal5

""" Astropy coordinate class for the Palomar 5 stream coordinate system """

# Third-party
import numpy as np

import astropy.units as u
import astropy.coordinates as coord
from astropy.coordinates import frame_transform_graph
from astropy.coordinates.matrix_utilities import matrix_transpose

__all__ = ["Pal5PriceWhelan18", "Pal5"]

[docs]class Pal5PriceWhelan18(coord.BaseCoordinateFrame): """ A Heliocentric spherical coordinate system defined by the orbit of the Pal 5 stream by A. Price-Whelan (2018). 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 Pal 5's orbit. phi2 : angle_like, optional, must be keyword The latitude-like angle corresponding to Pal 5'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 Pal 5 stream's orbit. pm_phi2 : :class:`~astropy.units.Quantity`, optional, must be keyword The proper motion in the latitude-like direction perpendicular to the Pal 5 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) r.lon.wrap_angle = self._default_wrap_angle return r
represent_as.__doc__ = coord.BaseCoordinateFrame.represent_as.__doc__
# Rotation matrix defined by trying to align the stream to the equator R = np.array([[-0.65019243, -0.75969758, -0.01045969], [-0.62969142, 0.54652698, -0.55208422], [0.42513354, -0.3523746, -0.83372274]]) # Extra rotation to put the cluster center at (0, 0) R2 = np.array([[9.99938314e-01, 1.57847502e-03, -1.09943927e-02], [-1.57837962e-03, 9.99998754e-01, 1.73543959e-05], [1.09944064e-02, 0.00000000e+00, 9.99939560e-01]]) R = R2 @ R @frame_transform_graph.transform(coord.StaticMatrixTransform, coord.ICRS, Pal5PriceWhelan18) def icrs_to_pal5(): """ Compute the transformation from Galactic spherical to heliocentric Pal 5 coordinates. """ return R @frame_transform_graph.transform(coord.StaticMatrixTransform, Pal5PriceWhelan18, coord.ICRS) def pal5_to_icrs(): """ Compute the transformation from heliocentric Pal 5 coordinates to spherical Galactic. """ return matrix_transpose(icrs_to_pal5()) # TODO: remove this in next version class Pal5(Pal5PriceWhelan18): def __init__(self, *args, **kwargs): import warnings warnings.warn("This frame is deprecated. Use Pal5PriceWhelan18 " "instead.", DeprecationWarning) super().__init__(*args, **kwargs) trans = frame_transform_graph.get_transform(Pal5PriceWhelan18, coord.ICRS).transforms[0] frame_transform_graph.add_transform(Pal5, coord.ICRS, trans) trans = frame_transform_graph.get_transform(coord.ICRS, Pal5PriceWhelan18).transforms[0] frame_transform_graph.add_transform(coord.ICRS, Pal5, trans)