Abstract
Using three samples of early-type galaxies in a magnitude range of ~5.5 mag, we analyse the behaviour of the Faber-Jackson relation coefficients as a function of the magnitude range where galaxies are selected. The coefficients depend on the brightness of galaxies and on the width of the magnitude range. These dependencies are due to selection effects and intrinsic galaxy properties. The intrinsic dispersion of the Faber-Jackson relation changes progressively with luminosity, with bright (relative to faint) galaxies having a significantly smaller dispersion.
