M-sigma relation

The M-sigma relation (M-σ relation) is a relation between the velocity dispersion of stars in the center of a galaxy and the mass of the central supermassive black hole (SMBH). It is empirical, derived from observation and subject to future improved calibration. It has been used as a means of determining the SMBH mass. Early version:

  M             σ
————— ≈ 3.1(——————————)4
108M☉       200 km s-1

Newer studies and analysis have adjusted the constant factor and exponent.