Bautz–Morgan classification

The Bautz–Morgan classification was developed in 1970 by Laura P. Bautz and William Wilson Morgan to categorize galaxy clusters based on their morphology.[1] It defines three main types: I, II, and III. Intermediate types (I-II, II-III) are also allowed. A type IV was initially proposed, but later redacted before the final paper was published.[2]

Classification

• A type I cluster is dominated by a bright, large, supermassive cD galaxy; for example Abell 2029 and Abell 2199.
• A type II cluster contains elliptical galaxies whose brightness relative to the cluster is intermediate to that of type I and type III. The Coma Cluster is an example of a type II.
• A type III cluster has no remarkable members, such as the Virgo Cluster. Type III has two subdivisions, type IIIE and type IIIS
  • Type IIIE clusters do not contain many giant spirals
  • Type IIIS clusters contain many giant spirals
• The deprecated type IV was for clusters whose brightest members were predominantly spirals.[2]

Examples

	Example	Type	Notes
	Abell 2199	Type I
	Abell S740	Type I-II
	Coma Cluster	Type II
	Abell 1689	Type II-III
	Virgo Cluster	Type III
		Type IIIS
		Type IIIE

See also

• Active galactic nucleus
• Galaxy morphological classification
• List of Abell clusters
• Planet
• Stellar classification

References

1. Bautz, L. P.; Morgan, W. W. (December 1970). "On the Classification of the Forms of Clusters of Galaxies" (PDF). Astrophysical Journal. 162: L149. Bibcode:1970ApJ...162L.149B. doi:10.1086/180643. A&AA ID. AAA004.160.015. Retrieved March 10, 2012.
2. Bautz, Laura P.; Morgan, W. W. (September 1970). "Preliminary Classification of Clusters of Galaxies" (PDF). Bulletin of the American Astronomical Society. 2: 294. Bibcode:1970BAAS....2R.294B. A&AA ID. AAA004.160.006. Retrieved March 10, 2012.