Tuesday, February 15, 2011, 3:45pm, Science Building 110
The Largest Galaxies in the Universe
Students Luke Leisman and David Sebald and Prof. Deb Haarsma
You may think our Milky Way galaxy is vast, since it contains billions of stars, yet it is dwarfed by a Brightest Cluster Galaxy (BCG). A BCG contains trillions of stars and has the mass of a hundred normal galaxies. The BCG is usually easy to spot among the many galaxies in a galaxy cluster because of its central position, large mass, and unique profile. The profile of a BCG fades very gradually from the bright center to the diffuse edges, while normal elliptical galaxies fade more quickly with radius. In this work we measure the brightness and profiles of galaxies in 74 clusters. Further, we develop an algorithm to identify the correct galaxy as the BCG even in ambiguous cases; our algorithm selects a more uniform sample than common methods used in the literature. The correct identification of BCGs plays an important role when studying correlations between BCG properties and the properties of the hot diffuse gas filling the space between the galaxies. These correlations, in turn, inform our understanding of the formation history of BCGs and their host clusters.