galactic halo

A galactic halo is a region around the visible part (bulk of the stars) of a galaxy, comprising of less visible parts of the same gravitationally-bound structure. The galactic halo includes:

• The dark matter halo.
• Gas/plasma - both any diffuse medium (the galactic corona), and individual clouds, such as high-velocity clouds.
• Occasional stars (the stellar halo).
• Possible additional globular clusters.
• Satellite galaxies (but I speculate one could be gravitationally-bound, yet beyond what is otherwise-termed the galactic halo).
• Dust.

(Note that in many phrases, the word galactic is taken to imply our galaxy, Milky Way, but the phrase galactic halo has been applied to galaxies in general.)