# Galactic¶

class astropy.coordinates.Galactic(*args, copy=True, representation_type=None, differential_type=None, **kwargs)[source]

A coordinate or frame in the Galactic coordinate system.

This frame is used in a variety of Galactic contexts because it has as its x-y plane the plane of the Milky Way. The positive x direction (i.e., the l=0, b=0 direction) points to the center of the Milky Way and the z-axis points toward the North Galactic Pole (following the IAU’s 1958 definition [R07ebe87fe85e-1]). However, unlike the Galactocentric frame, the origin of this frame in 3D space is the solar system barycenter, not the center of the Milky Way.

Parameters
dataBaseRepresentation subclass instance

A representation object or None to have no data (or use the coordinate component arguments, see below).

lAngle, optional, must be keyword

The Galactic longitude for this object (b must also be given and representation must be None).

bAngle, optional, must be keyword

The Galactic latitude for this object (l must also be given and representation must be None).

distanceQuantity, optional, must be keyword

The Distance for this object along the line-of-sight.

pm_l_cosbQuantity, optional, must be keyword

The proper motion in Galactic longitude (including the cos(b) term) for this object (pm_b must also be given).

pm_bQuantity, optional, must be keyword

The proper motion in Galactic latitude for this object (pm_l_cosb must also be given).

radial_velocityQuantity, optional, must be keyword

The radial velocity of this object.

representation_typeBaseRepresentation subclass, str, optional

A representation class or string name of a representation class. This sets the expected input representation class, thereby changing the expected keyword arguments for the data passed in. For example, passing representation_type='cartesian' will make the classes expect position data with cartesian names, i.e. x, y, z in most cases unless overriden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

differential_typeBaseDifferential subclass, str, dict, optional

A differential class or dictionary of differential classes (currently only a velocity differential with key ‘s’ is supported). This sets the expected input differential class, thereby changing the expected keyword arguments of the data passed in. For example, passing differential_type='cartesian' will make the classes expect velocity data with the argument names v_x, v_y, v_z unless overriden via frame_specific_representation_info. To see this frame’s names, check out <this frame>().representation_info.

copybool, optional

If True (default), make copies of the input coordinate arrays. Can only be passed in as a keyword argument.

Notes

R07ebe87fe85e-1

Blaauw, A.; Gum, C. S.; Pawsey, J. L.; Westerhout, G. (1960), “The new I.A.U. system of galactic coordinates (1958 revision),” MNRAS, Vol 121, pp.123.

Attributes Summary

Attributes Documentation

default_differential
default_representation
frame_specific_representation_info
name = 'galactic'