Do galaxy clusters follow De Vaucouleurs' law? Do galaxy clusters follow De Vaucouleurs' law? If objects in the universe are built hierarchically, wouldn't one expect a galaxy cluster that is roughly spherical to follow the same profile as an elliptical galaxy?
 A: They do indeed.
This page is a good starting point for further reading; it also leads to de Vaucouleurs (1948), in which de Vaucouleurs applies his eponymous relation to galaxy clusters. He uses a density profile
$$\sigma_b=\sigma_0\exp\left[-7.67\left(b/r_e\right)^{1/4}\right]$$
where $r_e$ is the radius such that one half of all galaxies lie at radii $b\leq r$. The similarity to the common logarithmic form of the law for galaxies should be apparent; re-arranging, it comes to
$$\log \sigma_b=\log \sigma_b-7.67\left(b/r_e\right)^{1/4}$$
De Vaucouleurs' application is the only one I can find at present. Mellier & Mathez (1986) applied the cluster version of de Vaucouleurs' Law to the Coma cluster
Related models, such as the fundamental plane, have also been fitted to galaxy clusters; see Marmo et al. (2004) and Schaeffer et al. (1993) for some interesting investigations into this.
A: I'm really hoping someone else will chime in, but here's what I've found on my own.  These fellows tried to fit the Coma Cluster into a NFW profile.  They referenced an earlier, apparently seminal work by Kent and Gunn.  Kent and Gunn attempted to fit the cluster into a inverse r-squared law (probably due to the fact that they used the inverse r-squared to select the members of the cluster).  The general form of their law is:
$$μ = \frac{μ_0}{ 1 + \left(\frac{r}{r_e}\right)^2}$$
Again, I'd love to see a respectable article where someone demonstrates a fit of a galaxy cluster to either a de Vaucouleurs or Sersic profile.
