Einasto

Einasto is a surname of Estonian origin. Notable individuals with this name include Jaan Einasto (1929–2019), an Estonian astrophysicist who helped advance the study of the large-scale structure of the universe and the distribution of matter in galaxies. His work contributed to the development of models describing how matter is distributed in astronomical systems, and he is associated with the concept of dark matter through observational and theoretical research.

The Einasto profile is a model for the three-dimensional density of stellar systems and dark matter halos. It has the form ρ(r) = ρ_e exp{-d_n[(r/r_e)^{1/n} - 1]}, where n is a shape parameter, r_e a scale radius, and ρ_e the density at r_e. The constant d_n depends on n and ensures a chosen relation between radius and enclosed mass. The profile yields a continuously varying slope and is flexible enough to fit a range of inner and outer density shapes.

It is widely used in astrophysics and cosmology for fitting simulated halos and galaxy light distributions. It often provides better fits than older models such as de Vaucouleurs or NFW, especially in the inner regions. The Einasto profile is part of a broader family of models used to describe density and brightness profiles in astronomical systems.