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

__all__ = ["Pal5PriceWhelan18"]


[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) if hasattr(r, "lon"): 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, 0.00000000e00, 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 icrs_to_pal5().T