Structures of Regular Clusters
Bahcall (1977) describes distributions as
truncated isothermal distributions:
Where f(r) is the projected distribution
normalized to 1 at r=0, and C is a constant
that makes N(r) = 0 at some radius.  Results
in steepening distribution in outer regions vs.
pure isothermal soultion.
R1/2 = 150-400 kpc (220 kpc for Coma)