Galactic

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

Bases: BaseCoordinateFrame

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 [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, keyword-only

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

bAngle, optional, keyword-only

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

distanceQuantity [:ref: ‘length’], optional, keyword-only

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

pm_l_cosbQuantity [:ref: ‘angular speed’], optional, keyword-only

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

pm_bQuantity [:ref: ‘angular speed’], optional, keyword-only

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

radial_velocityQuantity [:ref: ‘speed’], optional, keyword-only

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 overridden 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 overridden 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

[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

default_differential	Default representation for differential data (e.g., velocity)
default_representation	Default representation for position data
frame_attributes
frame_specific_representation_info	Mapping for frame-specific component names
name

Attributes Documentation

default_differential

Default representation for differential data (e.g., velocity)

default_representation

Default representation for position data

frame_attributes = {}

frame_specific_representation_info

Mapping for frame-specific component names

name = 'galactic'