The radius of the maximum circular velocity (confusingly sometimes also referred to as R max ) can be found from the maximum of M ( r ) / r as R c i r c max = α α R s where α α ≈ ≈ 2.16258 is the positive root of ln ⁡ ⁡ ( 1 + α α ) = α α ( 1 + 2 α α ) ( 1 + α α ) 2 . Maximum circular velocity is also related to the characteristic density and length scale of NFW profile: V c i r c max ≈ ≈ 1.64 R s G ρ ρ s