Centauras A – M83 Group
Within the Hydra, Centaurus, and Virgo constellations a complex group of galaxies resides called Centaurus A/M83. There are two subgroups within Centaurus A/M83. The first is Cen A, at a distance of 11.9 Million Light Years, is centered around Centaurus A, a close by radio galaxy. The other subgroup, M83, is at a distance of 14.9 Million Light Years and is centered around the Messier 83. Since there are two subgroups Centaurus is sometimes identified as one group and sometimes two, it will be referenced as Centaurus A Group or M83 Group. Since all the galaxies around those two are so physically close together both subgroups appear not to be moving relative to each other. The Centaurus A/M83 Group is part of the Virgo Supercluster.
Most of the brightest group members were identified in early galaxy group surveys, but many of the dwarf galaxies in the group were not identified until more intensive studies were completed. Optical images from the UK Schmidt Telescope as well as hydrogen line emission from the Parkes Radio Telescope helped identify 20 dwarf galaxies as members of the group. Through blind radio survey of hydrogen spectral line emission five uncatalogued galaxies in the group were found. The HIDEEP survey, a more intensive radio survey, identified an additional dwarf galaxy as a group member. 20 more candidate objects were added to the group from later optical surveys. The Cen A group membership of NGC 5011C was established in 2007. Even though the stellar system is listed with a NGC number its true identity was hidden due to confusion over coordinates and incorrect redshifts in the literature.