1.2 Thin-Disk Gravitational Models with Bulge Added
For a thin rotating galactic disk, we impose a balance between the Newtonian gravitational forces and centrifugal forces at each and every point. Because the gravitational ﬁeld of a thin disk is not spherically symmetric, the orbital velocity law is not applicable.
As illustrated by Feng & Gallo  , an axisymmetric thin disk gravitational model successfully describes the basic rotational dynamics of mature spiral galaxies with a mass density decreasing from the center to periphery. And the calculated total galactic masses are in good agreement with star count data.