On the shape of the light profiles of early-type galaxies

Abstract

We have obtained the best fit to the light profiles of a luminosity limited sample of elliptical and S0 galaxies with a power law \rn, letting the exponent remain free rather than keeping it fixed at $1/n=1/4$ as in the well known \GV formula. The introduction of a free parameter in the fitting formula (ranging from $n=0.5$ for $<\re>=0.3$ kpc to $n=16$ for $<\re>=25$ kpc) is justified by the existence of a good correlation between $n$ and the global galaxian parameters, such as total luminosity and scale-radius. This result seems to be in line with the segregation of properties between the `ordinary&#39; and `bright&#39; families of early-type galaxies, and has consequence for the claimed independence of the shape of galaxy profiles with respect to the Fundamental Plane parameters.