A stellar halo is the extended, approximately spheroidal stellar population surrounding a galaxy. It differs from the total dark matter halo. If its outer luminosity density is , its projected light follows the projection of a spherical power-law emissivity and scales as away from breaks and outer truncation.
Intracluster light comes from stars bound to a cluster rather than an individual galaxy. Tidal stripping and disruption of member systems can create extended diffuse light and substructure. Distinguishing this component from the outer envelope of the central galaxy depends on the adopted dynamical or photometric definition.
A stellar stream is a correlated collection of stars commonly originating in the disruption of a bound progenitor. Phase mixing can erase spatial contrast while leaving coherence in orbital integrals. Such fossil debris constrains a galaxy's past accretion, although not every stream is from a galaxy: star clusters also produce streams.
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The term "stellar halo" refers to a roughly spherical region surrounding a galaxy, composed of stars, globular clusters, and dark matter. The stellar halo typically contains older stars and is less dense than the main disk of the galaxy. In our Milky Way, for instance, the stellar halo extends well beyond the visible disk and is thought to be a remnant of the early stages of galaxy formation and accretion of smaller galaxies and star clusters.