Core and power-law elliptical galaxies

Bright elliptical galaxies commonly have a shallow central surface-brightness cusp inside a break radius, whereas many less luminous elliptical galaxies have a steep cusp continuing inward. The latter can have many more luminous tracers at a fixed small radius, helping central black hole dynamical measurements. This empirical distinction is not a universal classification by mass alone. Measurements of central galaxy profiles quantify the contrast.