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A dwarf spheroidal galaxy is a faint, diffuse, largely pressure-supported galaxy with little gas. A large dynamical mass-to-light ratio commonly indicates dark matter, subject to assumptions of equilibrium, member selection, and binary-star corrections. Its stellar light and total mass need not share one density profile.

The Faber-Jackson relation is an empirical correlation between luminosity and stellar velocity dispersion for elliptical galaxies, approximately $L\propto {\sigma }^4$ in its classical form. Slope, scatter, sample and band matter. A heuristic combines $M\propto {\sigma }^{2}R$, common mass-to-light ratio, and common characteristic surface brightness $L/R^2$. The luminosity-dispersion correlation alone does not imply those auxiliary assumptions, and extrapolation to a dwarf spheroidal galaxy is not guaranteed.