Hubble-Reynolds Law

Not to be confused with Hubble's Law which relates galaxy redshifts and distances.

The Hubble-Reynolds Law models the surface brightness of elliptical galaxies as

$I(R) = \frac{I_0}{(1%2BR/R_H)^2}$

Where $I(R)$ is the surface brightness at radius $R$ , $I_0$ is the central brightness, and $R_H$ is the radius at which the surface brightness is diminished by a factor of 1/4. It is asymptotically similar to the de Vaucouleurs Law which is a special case of the Sérsic Law for elliptical galaxies.^[1]

References

^ Binney & Tremaine. Galactic Dynamics 2008.