galaxy subgroup

The term subgroup (for galaxy subgroup) is used for a subgroup of a galaxy group or galaxy cluster such as a significant galaxy plus its satellite galaxies. That sort of grouping is often determined by proximity but may be checked using mass and velocity determinations, and in some cases, metallicity determinations can assist. Within the Local Group, the term is used for the Milky Way subgroup, the Andromeda subgroup (aka M31 subgroup) and the Triangulum subgroup (aka M33 subgroup).