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| Centaurus A Group | |
|---|---|
| Name | Centaurus A Group |
| Epoch | J2000 |
| Members | ~50 |
| Major components | Centaurus A, M83 subgroup |
| Distance | ~11–13 Mly |
| Constell | Centaurus |
Centaurus A Group
The Centaurus A Group is a nearby galaxy group centered on the radio galaxy Centaurus A and including the spiral M83; it lies in the southern constellation Centaurus and forms part of the larger Virgo Supercluster complex near the Local Group and the Fornax Cluster. The group contains a mix of massive elliptical, lenticular, and spiral galaxies together with numerous dwarf spheroidal and dwarf irregular systems; it has been studied via optical surveys, radio observations of neutral hydrogen, and X-ray imaging with observatories including Hubble Space Telescope, Chandra X-ray Observatory, Very Large Array, and Australian Telescope Compact Array.
The Centaurus A Group comprises two principal concentrations often referred to as the Centaurus A subgroup, dominated by Centaurus A (NGC 5128), and the M83 subgroup, dominated by Messier 83 (NGC 5236). Located at distances around 3.5–4.0 megaparsecs from the Milky Way, the group overlaps in projection with the nearby M83 Group designation used in some surveys; its membership and extent were refined through redshift surveys by teams using instruments such as the Anglo-Australian Telescope, the European Southern Observatory facilities, and the Parkes Observatory. The group plays a key role in mapping local large-scale structure alongside the Local Void, the Centaurus Supercluster region, and connections to the Sculptor Group and NGC 5128-centric flows.
Prominent members include the radio-loud elliptical Centaurus A (NGC 5128), the barred spiral Messier 83 (NGC 5236), the lenticular NGC 4945, the spiral NGC 5253, and dwarf systems such as NGC 3109, IC 4247, ESO 270-017, and ESO 381-018; other cataloged members appear in the New General Catalogue (NGC), the Index Catalogue, the Fornax Cluster-adjacent lists, and modern compilations like the Two Micron All Sky Survey (2MASS) Extended Source Catalog. Surveys by the Sloan Digital Sky Survey did not fully cover this southern field, so membership identification relied heavily on targeted programs by the European Southern Observatory, the Cerro Tololo Inter-American Observatory, and the Anglo-Australian Observatory. Dwarf spheroidals and dwarf irregulars such as ESO 269-66, KK 196, and CenA-MM-Dw1 have been identified via deep imaging with Hubble Space Telescope and wide-field detectors like the Dark Energy Camera.
Kinematic studies using optical redshifts from the Anglo-Australian Telescope and HI velocity fields from the Australia Telescope Compact Array and the Green Bank Telescope reveal a kinematically complex group with substructures, including a dynamically colder M83 subgroup and a more massive Centaurus A subgroup. Mass estimates derived from virial theorem applications and X-ray halo measurements obtained with XMM-Newton and Chandra X-ray Observatory indicate total group masses of order 10^12–10^13 solar masses, comparable to that of the Local Group. Numerical simulations carried out on supercomputing resources at institutions like Max Planck Institute for Astrophysics and Harvard-Smithsonian Center for Astrophysics model tidal interactions, orbit decay, and group assembly history, constrained by proper motion studies and distance ladders anchored to Cepheid variable and Tip of the Red Giant Branch measurements from Hubble Space Telescope programs.
Star formation rates and interstellar medium properties in Centaurus A Group members have been probed using multiwavelength campaigns: ultraviolet imaging with GALEX, infrared mapping with Spitzer Space Telescope and Herschel Space Observatory, radio continuum with Very Large Array, and CO molecular gas surveys at Atacama Pathfinder Experiment and ALMA. Active star-forming regions in Messier 83 and NGC 5253 contrast with the largely quenched stellar populations of the giant elliptical Centaurus A, whose central active nucleus and jet, studied by European Southern Observatory and Very Long Baseline Array programs, affect circumgalactic gas via feedback. Observations of neutral hydrogen (HI) reveal tidal tails, warps, and intergalactic HI clouds attributable to past mergers and interactions, with chemical abundances measured through optical spectroscopy at facilities such as Keck Observatory and Very Large Telescope informing enrichment histories.
The Centaurus A Group occupies a strategic location near the Local Group and the Sculptor Group and partakes in the cosmic flows feeding the Virgo Supercluster and the so-called "Local Sheet"; peculiar velocity studies using distance indicators from programs led by teams at Carnegie Institution for Science and Space Telescope Science Institute show coherent motions toward mass concentrations including the Great Attractor region associated with the Norma Cluster. Tidal interactions and past close encounters between Centaurus A Group members have led to satellite capture and dwarf galaxy disruption, processes analogous to those inferred for the Milky Way–Andromeda Galaxy system. The group's environment influences the fate of its dwarfs through ram-pressure stripping in intragroup medium detected in X-rays by XMM-Newton and Chandra X-ray Observatory.
Historical identification of bright members like Centaurus A and Messier 83 dates to early telescopic catalogs by observers such as John Herschel and entries in the New General Catalogue compiled by John Louis Emil Dreyer. Systematic recognition of the group as a gravitationally bound system emerged from 20th-century redshift surveys by teams at the Mount Stromlo Observatory and the Harvard College Observatory, with modern membership catalogs refined through HI blind surveys by the Parkes Observatory HIPASS project and optical follow-ups using Hubble Space Telescope for precise distances. Continued discovery of faint satellites has accelerated with deep imaging surveys executed by collaborations involving European Southern Observatory and the Carnegie Institution for Science, and theoretical interpretation has advanced through work at institutions including the Max Planck Society and Institute for Astronomy, Cambridge.
Category:Galaxy groups