Type: Poster
Session: Posters (Wednesday & Thursday)
Author: Yen-Ting Lin

Abstract: The most massive galaxy in a cluster, often called the brightest cluster galaxy (BCG), appears to have properties different from giant elliptical galaxies in terms of having very extended stellar envelop, exhibiting a different size-mass relation, higher duty cycle of central supermassive black hole activities, etc. The stellar mass of a BCG is also found to be correlated with the total mass of its host cluster, indicating the formation of BCGs may be linked to that of the clusters. It is natural to ask: whether BCGs are simply the statistical extreme of the (cluster) galaxy stellar mass function, or a distinct population from the rest of cluster galaxies? We have shown that, using two different statistical tests (the Tremaine-Richstone 1977 statistics and the one proposed by Lin, Ostriker & Miller 2010), BCGs are a distinct population ("special") out to redshift z~1. In this contribution, we extend the investigation to higher redshifts: using two observed cluster samples, we have found the BCGs remain special to z~2. To understand whether BCGs were born special or started similarly as other galaxies but gradually became special due to their special location within the host clusters, we use the IllustrisTNG300 simulation and follow the evolution of model BCGs to z~4, an upper limit set by the resolution of the simulation. It is found that BCGs remain special even at z~4. We discuss possible formation channels of this special species of galaxies.