BCGs can be defined in different ways and are often synonymous with brightest central galaxies or even cD galaxies (galaxies with optically extended light envelopes). BCGs are the most massive galaxies and their formation and evolution are a popular and current research topic (Linden et al. 2006, Bernardi et al. 2006, Lauer et al. 2006). They have been studied for some time (Sandage 1972, Ostriker & Tremain 1975, White 1976, Thuan & Romanishin 1981, Merritt 1985, Postman and Lauer 1995, among many others).

In this VO research example, our aim is to take a list of galaxies known to lie within the footprint of the SDSS, which provides us with the possibility that some of these galaxies will have measured spectra from the SDSS spectroscopic pipeline. Thus, there is some prerequisite knowledge: 1) Many bright SDSS galaxies have spectra with measured emission line properties; 2) Our catalog of Brightest Cluster Galaxies has some overlap with the SDSS footprint. Taken together, we can crossmatch our catalog to the SDSS spectroscopic galaxy data in order to extract any available emission-line information.