Abstract:  Galaxy groups and clusters are among the oldest and most massive structures in the universe, housing enormous elliptical galaxies in their centers. A subset of these galaxy systems, known as fossil systems, take this to the extreme by hosting overly-luminous central galaxies compared to the systemʼs size. The origin of fossil systems has been debated for many years. Are they formed differently than other groups, or is a fossil merely a transitory phase in the normal evolution of a galaxy system? Are fossil systems born or made? The discovery of the Cheshire Cat fossil group progenitor (Irwin et al. 2015) shows that fossil systems can still be formed, demonstrating that we can find the progenitors to fossil systems today. Finding more fossil progenitors would allow us to determine which formation mechanisms exist for fossil systems. By studying the CASSOWARY catalog of strong gravitational lensing events in the Sloan Digital Sky Survey, we identified 18 additional fossil progenitors along with some of their properties. We present our findings of these progenitors, possible implications for fossil system formation, and preliminary X-ray data for some of the most promising systems.

Host: Eric Miller