Freeman law explained

The Freeman law is a statement in astronomy which says that disk galaxies have the same surface brightness, Σ at the center. It was described in 1970 by Ken Freeman.[1] [2]

More recently it has been argued that the Freeman law is an effect of selection bias.[3] However, after accounting for selection effects, the Freeman law was confirmed in the year 2010 for a sample of 30000 Sloan Digital Sky Survey galaxy images.[4] It can be used with the Tully–Fisher relation to determine the luminosity and therefore distance of an observed galaxy.

The Freeman law is sometimes called the Fish-Freeman effect.[5]

Fish law

The Fish law (or Fish's law) in astronomy is the analogue for the Freeman law with disk galaxies replaced by elliptical galaxies. It was described in 1964 by Robert A. Fish based on photometric results for 29 elliptical galaxies.[6]

Modified Newtonian Dynamics (MOND)

According to Brada and Milgrom,[7]

References

  1. astro-ph/9505062. McGaugh. S. S. Galaxy Selection and the Surface Brightness Distribution. The Astronomical Journal. 110. 1995. 573. Bothun. G. D. Schombert. J. M. 1995. 10.1086/117543. 1995AJ....110..573M. 119527623.
  2. Freeman, Kenneth C.. On the disks of spiral and S0 galaxies. The Astrophysical Journal. 160. 3. 1970. 811–830. 1970ApJ...160..811F. 10.1086/150474. free.
  3. Minnesota State University, "Web site: Archived copy . 2008-01-11 . dead . https://web.archive.org/web/20070706235131/http://odin.physastro.mnsu.edu/~eskridge/astr225/week10.html . 2007-07-06 . "
  4. 1009.2692. Fathi. Kambiz. Revisiting the Scale Length-mu0 Plane and the Freeman Law in the Local Universe. The Astrophysical Journal. 722. L120–L125. 2010. 1. 10.1088/2041-8205/722/1/L120. 2010ApJ...722L.120F. 119208149.
  5. Disney, M.. Phillipps, S.. 1983. The visibility of galaxies as a function of central surface brightness. Monthly Notices of the Royal Astronomical Society. 205. 4. 1253–1265. 10.1093/mnras/205.4.1253. 1983MNRAS.205.1253D. free.
  6. Fish, Robert A.. A Mass-Potential Relationship in Elliptical Galaxies and Some Inferences Concerning the Formation and Evolution of Galaxies. The Astrophysical Journal. 139. 1. 1964. 284–305. 1964ApJ...139..284F. 10.1086/147753. free.
  7. Brada, Rafael. Milgrom, Mordehai. The modified dynamics (MOND) predicts an absolute maximum to the acceleration produced by 'dark halos'. The Astrophysical Journal. 512. 17. L17. December 1998. astro-ph/9812117. 10.1086/311871. 1999ApJ...512L..17B. 117804800.

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