LEAPS-MPS: The tiniest galaxies in the Universe as testbeds of fundamental physics

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This award is funded in whole or in part under the American Rescue Plan Act of 2021 (Public Law 117-2). One of the open fundamental questions about the universe is the fraction of matter that is ‘cold dark matter,’ which does not interact with light. This fraction, called LAMBDA_CDM, governs how galaxies form and evolve in the standard cosmological model. While the model works very well for larger galaxies like the Milky Way, there are challenges for smaller galaxies, such as dwarf galaxies. This project will employ undergraduate students at a Hispanic Serving Institution in cutting-edge cosmological research using the latest models to explore fundamental questions about our universe, such as ‘what is the nature of dark matter?’ The students will apply these models to low-mass galaxies to make predictions that will be testable with future observations. Students will be recruited through the Cal-Bridge Program, which focuses on students from under-represented backgrounds. Students will use observations of ultra-faint dwarf galaxies to constrain cosmological models of dwarf galaxy formation around larger galaxies. They will produce testable predictions of the number of dwarf galaxies around a Milky Way-size galaxy for given input parameters such as LAMBDA_CDM, which will place constraints on the amount of cold dark matter in the Universe. They will also place limits on the sources and timing of the cosmic reionizing background, make predictions for the effect of dwarf galaxy major mergers on stellar kinematics, and test the effect of the presence of a Milky Way-size galaxy on the results of these same experiments.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.