adding stand alone gala files

Author: abostroem

student_download/gd1.py

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+"""Astropy coordinate class for the GD-1 coordinate system"""
+
+import astropy.coordinates as coord
+import astropy.units as u
+import numpy as np
+from astropy.coordinates import frame_transform_graph
+
+__all__ = ["GD1Koposov10"]
+
+
+class GD1Koposov10(coord.BaseCoordinateFrame):
+    """
+    A Heliocentric spherical coordinate system defined by the orbit of the GD1 stream,
+    as described in Koposov et al. 2010 (see: `<http://arxiv.org/abs/0907.1085>`_).
+
+    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 GD-1's orbit.
+    phi2 : angle_like, optional, must be keyword
+        The latitude-like angle corresponding to GD-1'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 GD-1 stream's orbit.
+    pm_phi2 : :class:`~astropy.units.Quantity`, optional, must be keyword
+        The proper motion in the latitude-like direction perpendicular to the
+        GD-1 stream's orbit.
+    radial_velocity : :class:`~astropy.units.Quantity`, optional, must be keyword
+        The radial velocity 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
+    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 as defined in the Appendix of Koposov et al. (2010)
+R = np.array(
+    [
+        [-0.4776303088, -0.1738432154, 0.8611897727],
+        [0.510844589, -0.8524449229, 0.111245042],
+        [0.7147776536, 0.4930681392, 0.4959603976],
+    ]
+)
+
+
+@frame_transform_graph.transform(coord.StaticMatrixTransform, coord.ICRS, GD1Koposov10)
+def icrs_to_gd1():
+    """
+    Compute the transformation from ICRS spherical to heliocentric GD-1 coordinates.
+    """
+    return R
+
+
+@frame_transform_graph.transform(coord.StaticMatrixTransform, GD1Koposov10, coord.ICRS)
+def gd1_to_icrs():
+    """
+    Compute the transformation from heliocentric GD-1 coordinates to ICRS spherical.
+    """
+    return icrs_to_gd1().T

student_download/reflex.py

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+import astropy.coordinates as coord
+
+__all__ = ["reflex_correct"]
+
+
+def reflex_correct(coords, galactocentric_frame=None):
+    """Correct the input Astropy coordinate object for solar reflex motion.
+
+    The input coordinate instance must have distance and radial velocity information.
+    So, if the radial velocity is not known, fill the radial velocity values with zeros
+    to reflex-correct the proper motions.
+
+    Parameters
+    ----------
+    coords : `~astropy.coordinates.SkyCoord`
+        The Astropy coordinate object with position and velocity information.
+    galactocentric_frame : `~astropy.coordinates.Galactocentric` (optional)
+        To change properties of the Galactocentric frame, like the height of the
+        sun above the midplane, or the velocity of the sun in a Galactocentric
+        intertial frame, set arguments of the
+        `~astropy.coordinates.Galactocentric` object and pass in to this
+        function with your coordinates.
+
+    Returns
+    -------
+    coords : `~astropy.coordinates.SkyCoord`
+        The coordinates in the same frame as input, but with solar motion
+        removed.
+
+    """
+    c = coord.SkyCoord(coords)
+
+    # If not specified, use the Astropy default Galactocentric frame
+    if galactocentric_frame is None:
+        galactocentric_frame = coord.Galactocentric()
+
+    v_sun = galactocentric_frame.galcen_v_sun
+
+    observed = c.transform_to(galactocentric_frame)
+    rep = observed.cartesian.without_differentials()
+    rep = rep.with_differentials(observed.cartesian.differentials["s"] + v_sun)
+    fr = galactocentric_frame.realize_frame(rep).transform_to(c.frame)
+    return coord.SkyCoord(fr)