>>> import astropy.coordinates as coord
>>> import astropy.units as u
>>> import gala.coordinates as gc

Stellar Stream Coordinate Frames

Also included in this subpackage are Astropy coordinate frame classes for transforming to Sagittarius and Orphan stream coordinates (as defined in the references below). These classes behave like the built-in astropy coordinates frames (e.g., ICRS or Galactic) and can be transformed to and from other astropy coordinate frames:

>>> c = coord.SkyCoord(ra=100.68458*u.degree, dec=41.26917*u.degree)
>>> c.transform_to(gc.Sagittarius) 
<SkyCoord (Sagittarius): (Lambda, Beta) in deg
    (179.58511054, -12.55845019)>
>>> s = gc.Sagittarius(Lambda=156.342*u.degree, Beta=1.1*u.degree)
>>> c = coord.SkyCoord(s)
>>> c.galactic 
<SkyCoord (Galactic): (l, b) in deg
    (182.5922090437946, -9.539692094685897)>

References

• A 2MASS All-Sky View of the Sagittarius Dwarf Galaxy: I. Morphology of the Sagittarius Core and Tidal Arms
• The Orbit of the Orphan Stream