Einasto profile

of a spherical stellar system varies with distance

Jaan Einasto introduced his model at a 1963 conference in Alma-Ata, Kazakhstan.

[1] The Einasto profile possesses a power law logarithmic slope of the form:

controls the degree of curvature of the profile.

This can be seen by computing the slope on a log-log plot:

, the more rapidly the slope varies with radius (see figure).

, which has a constant slope on a log-log plot.

Einasto's model has the same mathematical form as Sersic's law, which is used to describe the surface brightness (i.e. projected density) profile of galaxies, except that the Einasto model describes a spherically symmetric density distribution in 3 dimensions, whereas the Sersic law describes a circularly symmetric surface density distribution in two dimensions.

Einasto's model has been used to describe many types of system, including galaxies,[2] and dark matter halos.