Astrophysics (Index)About

cluster radius

(radius of a galaxy cluster)

A galaxy cluster's radius (cluster radius) is not distinct, and various criteria are used to define one, such as the extent of the extra mass density represented by the cluster. Some measures that are used:

The mass in question includes the cluster's intracluster medium and dark matter halo. Estimated proportions of these measures:

R500c:R200c:R200m:Rsp≈1:1.4:3:4

Distant galaxy clusters are often scaled in relation to the critical density at the redshift of the cluster, because there are galaxy cluster attributes that follow that scale. The commonly-used galaxy cluster radius value R500 indicates the radius that surrounds a volume whose mean density is 500 times the critical density at that redshift. Radii within the cluster can be usefully scaled as R/R500. Values used, based, e.g., on R500:

Other parameters can be defined similarly.


(galaxy clusters,measure,radius)
Further reading:
https://ui.adsabs.harvard.edu/abs/2015ApJ...810...36M/abstract
http://ned.ipac.caltech.edu/level5/Sept09/Bohringer/Bohringer3.html
https://ui.adsabs.harvard.edu/abs/2013SSRv..177..195R/abstract
https://ui.adsabs.harvard.edu/abs/2005ApJ...633..122H/abstract

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