Faber–Jackson relation

An empirical scaling relation linking an elliptical galaxy’s luminosity to approximately the fourth power of its central stellar velocity dispersion.

Stellar velocity dispersion: A measure of the spread in stars’ line-of-sight velocities within a stellar system. It is the measured kinematic quantity raised to the fourth power in the relation.
Sandra M. Faber: An American astronomer known for research on galaxies, cosmology, and large-scale structure. She co-discovered the relation through measurements of elliptical galaxies.
Distance indicator: An observable property or method used to estimate an astronomical object’s distance. Galaxy luminosity inferred from velocity dispersion can serve as a distance indicator.
Tully–Fisher relation: An empirical relation between a spiral galaxy’s luminosity and its rotational velocity. It is the corresponding luminosity–kinematics scaling for rotation-supported disk galaxies.
Virial theorem: A relation between the time-averaged kinetic and potential energies of a stable bound system. It helps explain why galaxy luminosity can scale with stellar speeds.
Robert Earl Jackson: An American astronomer who co-authored the 1976 study introducing the Faber–Jackson relation. His collaboration with Faber established the empirical luminosity–dispersion connection.
Hubble constant: The present-day rate of cosmic expansion, relating recession speed to distance on large scales. Distance estimates from the relation can contribute to measurements of cosmic expansion.
Kormendy relation: An empirical relation between the effective radius and mean surface brightness of elliptical galaxies. It relates structural properties rather than luminosity directly to velocity dispersion.
Mass-to-light ratio: The ratio of a system’s mass to its emitted luminosity in a specified band. Variations in this ratio help determine the observed slope and scatter.
1976: A year in the Gregorian calendar. The relation was reported in a landmark paper published that year.

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Sandra FaberRelated: Faber co-discovered this relation, which made stellar motions a tool for estimating galaxy luminosities.