Clusters of galaxies are key players in unraveling the mysteries behind galaxy formation and evolution, and understanding such mysteries is necessary to uncover how our Universe evolved and to learn how our own Milky Way Galaxy began. Galaxy clusters have long been considered active sites of galaxy evolution although the physical processes driving these transformations have yet to be established. Recent studies have revealed that, even at large distances from the cluster center, galaxy populations look different from those in the field, and they raise the possibility of cluster galaxy pre-processing in intermediate environments. Furthermore, as sample sizes have increased, the ubiquity of cluster mergers has become apparent, a natural consequence of a hierarchical universe where clusters represent the most massive virialized objects. This project investigates the effects that these events may have on the cluster galaxy population---effects that are currently not well understood.
Combining the recently completed Arizona Cluster Redshift Survey (ACReS)---an extensive, stellar-mass selected, wide-field spectroscopic survey---with existing multi-wavelength data (from X-rays to far-infrared), this project will study the connections between a cluster's hierarchical growth and the evolution of its baryonic components. The project's main objectives are the following: (1) to determine each cluster's dynamical state and correlate this with global properties of the cluster galaxy population, (2) to probe the mass distribution surrounding the clusters by identifying filamentary environments and by compiling a unique sample of infalling groups around clusters, and (3) to relate infalling galaxy properties to their local environments, thereby identifying the sites and requisite conditions for galaxy pre-processing in a large, uniform sample of clusters for the first time.
The broader impacts of this project include the following: (1) The investigators will create a companion web site for the ACReS project aimed at a wide audience that highlights the use of multi-wavelength and spectroscopic data for a deeper understanding of the Universe. The web site will be aggressively publicized to local school teachers for use in their classrooms. (2) The project will conduct workshops at the Mt. Lemmon SkyCenter for K-14 teachers to bring them into close contact with astronomers at The University of Arizona and bring the excitement of scientific discovery into Southern Arizona classrooms, where ethnic minorities make up to 70-80% of the student population. (3) The project will construct a database for ACReS clusters that will be released to the community at the end of the two year period to create a legacy for future cluster studies. (4) The principal investigator will train undergraduates and a postdoctoral researcher.
