magnitude gaps

Inspired by some results shown by Milos Milosavljevic in his talk yesterday, Blanton and I tried to do a single-afternoon project on the distribution of magnitude gaps between first-ranked and second-ranked and between first-ranked and third-ranked galaxies in Berlind's groups. The distributions are barely different from what you would expect if galaxy groups are simply random, Poisson samplings of the relevant luminosity functions. We are trying to figure out just how different. The big picture is: Are the groups with very large magnitude gaps old "fossil groups" where the original members have all merged into the central galaxy, or are they just the random occurences you get from sampling the luminosity distribution randomly? We didn't finish, but we got everything ready for the quantitative analysis.