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Fundamental Plane
•Luminosities, surface brightness, central velocity distribution, (and others), are correlated, hence the term “fundamental plane.”  Ellipticals populate a plane in parameter space.  BIG area of research – very useful tool and helps us understand galaxies.
•Faber & Jackson (1976) is a classic in this area (you might want to look up and read this one):
•L ~ σx where x ≈4
•So, get dispersion from spectrum, get luminosity, and with magnitude get distance!