Testing SIDM with Realistic Galaxy Formation Simulations

University Of Oklahoma Norman Campus, Norman OK

Investigators

Abstract

This award funds the collaborative research activities of Professor Ferah Munshi at the University of Oklahoma. Most of the matter in our Universe resides in an unknown component, dark matter. We have learned this primarily by studying the gravitational interactions of galaxies. Therefore, astrophysical measurements are a compelling way of directly studying the properties of dark matter. The nature of dark matter remains one of the most important questions in physics. Gravitational evidence points to dark matter that is "cold", meaning that it moves slowly and therefore is probably a heavy particle. This is the Cold Dark Matter (CDM) model. However, decades of experimental effort to detect such a heavy particle have not yet yielded conclusive evidence. Also, the CDM model has faced challenges matching the observed properties of dwarf galaxies (galaxies smaller than our Milky Way). These problems have inspired alternative dark-matter models. One alternative model that may work well is Self-Interacting Dark Matter (SIDM). SIDM and CDM should yield different distributions of mass within dwarf galaxies, but this has not been modeled in detail. As part of her research, Professor Munshi will use state-of-the-art computer simulations to model dwarf galaxies with both the CDM model and the SIDM model. Data from these simulations will be evaluated against data from real galaxies in order to constrain the nature of dark matter. This research advances the scientific leadership of the United States in the understanding of dark matter. Moreover, this project will train future scientists, with the goal of diversifying the US technical workforce. An expanded and diversified scientific workforce helps to ensure that the US remains a leader in innovation and economic growth. More technically, the proposed research will result in a suite of high-resolution, state-of-the-art simulations of galaxy formation within the SIDM paradigm. SIDM preserves the large-scale success of CDM, while opening up the possibility of altering the small scales in testable ways using galaxy observations. The group will use the N-Body+SPH code ChaNGa to run a series of simulations. First will be "zoom" simulations of individual dwarf galaxies in order to test whether CDM of SIDM can reproduce the diverse range of rotation curves observed in real galaxies. These galaxies will be run in both CDM and SIDM. Second will be studies of "zoom" volumes that contain dozens of dwarfs from 1000 solar masses to 10^9 solar masses in order to directly compare the observed shapes of galaxies with those predicted in CDM vs. SIDM. Analytic models have shown that an SIDM model with an interaction cross-section of ~3 cm^2 g^-1 can reproduce the full range of galaxy rotation curves. This research will test this model across a range of galaxy simulations for the first time. The broader-impacts component of this project builds on the successful Pre-Major in Astronomy Program (Pre-MAP) at the University of Washington by establishing a Pre-Map-like first-year seminar at the University of Oklahoma through an existing "Introduction to Research" class, and will expand the program to include training more relevant to physics research in addition to astronomy. This program will not only develop a mentoring relationship between students and members of the Physics and Astronomy Department, but also utilize cohort-building activities to develop the students into a peer-support network for each other. Finally, this program will introduce the students to basic research tools and involve them in original research. This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.