Title: Fossil Groups and their luminosity functions
Author(s): L. Sodre Jr., R. Lopes de Oliveira, C. Mendes de Oliveira, 
E. Cypriano, R. Dupke, D. R. Bortoletto
Abstract:
Fossil Groups are groups (or clusters) of galaxies optically
dominated by an elliptical galaxy immersed in an extended and luminous 
X-ray halo, in which the magnitude gap between the two brightest galaxies 
within half of the virial radius is greater than 2 in the r-band. Recent
studies suggest that the central galaxies in Fossil Groups are most likely
formed by mergers of galaxies that had lost energy by dynamical friction, and
that the velocity dispersion and X-rays properties of these systems are
reminiscent of those of clusters, more than groups of galaxies. Here we report 
on the results of our search for new fossil groups and confirmation of
candidates suggested in the literature by acquiring spectroscopy with
Gemini/GMOS of the member galaxies. We also present a photometric study of 
the luminosity function of a sample of 10 group candidates using the SDSS 
database. A Schechter function describes well the individual luminosity 
functions, with an alpha parameter ranging from 0.5 to -1.5.  Our fossil 
groups have a range of masses and other properties ranging from groups 
to clusters.