Unified Modeling of Galaxy Populations in Clusters

Thomas Quinn, University of Washington

Usage Details

Understanding the history of galaxy and cluster formation fundamentally affects our knowledge of the Universe as a whole, and sets the context for our place within the Universe. This project will use Blue Waters to model the formation and evolution of a population of galaxies in a Coma-sized galaxy cluster, including their contribution to and interaction with the Intra-Cluster Medium (ICM). Modeling galaxies and the ICM in galaxy clusters is a formidable challenge. The morphology of the galaxies, and the energy and metal content of the gas is ultimately controlled by star formation processes that happen on molecular cloud scales of less than a million solar masses. On the other hand, total cluster masses exceed 10¹⁵ solar masses; hence a dynamic range in mass of over a billion is necessary for consistently modeling galaxies within this context. The investigation of such issues is appealing to many interested in science and even in society at large. In particular, the results of the project will be used in a program that will introduce the use of computer simulations in astrophysics to science pre-majors, in the hope of ultimately attracting underrepresented students into a STEM major.

Several advancements have now enabled the modeling of these systems. First is the availability of supercomputers like Blue Waters that can sustain petaflop calculations on real world problems. Second is the improvement of hydrodynamic modeling in Lagrangian codes. These improvements include better modeling of multiphase medium and the resulting instabilities, more accurate handling of high Mach number shocks, and better modeling of the sub-grid physics including growth and feedback from supermassive black holes. Finally these algorithm improvements have been implemented in codes that can scale to a large fraction of Blue Waters even with very clustered datasets. This project will use the highly scalable N-body/hydrodynamics code, ChaNGa, to model the formation and evolution of a population of galaxies in a Coma-sized galaxy cluster, including their contribution to and interaction with the ICM. This model will be compared to observations of cluster galaxies to understand the physical and temporal origin of their morphologies. The model ICM will be compared to X-ray and microwave (via the Sunyaev-Zeldovich effect) to understand the relation between these observables and the underlying gas properties. Finally, the overall mass distribution will be used to better understand how these clusters gravitationally lens background galaxies.