Collaborative Research: Reconstructing Primordial Density Fluctuations using Near-Field Cosmology

Faint dwarf galaxies are sensitive to dark matter and early universe physics. The investigators will develop a model that comprehensively predicts the population of dwarf galaxies surrounding the Milky Way as a function of dark matter properties and early universe dynamics. Comparing these predictions to the data will yield constraints on dark matter particle models and cosmic inflation. The key product of this work is an efficient and accurate model for the Milky Way’s dwarf galaxy population in non-standard cosmologies. This work will train early career researchers in broadly-applicable computational methods and support undergraduates from underrepresented groups in physics through the National Society of Black Physicists and Society for the Advancement of Chicanos/Hispanics and Native Americans in Science programs. Dwarf galaxies occupy the smallest dark matter halos that can form stars. These systems are extremely sensitive to unknown dark matter and early universe physics. To date, the faintest dwarf galaxies have exclusively been detected as satellites of the Milky Way. This situation presents a theoretical challenge: to discover fundamental physics in these data, we must model the specific formation history of our Galaxy’s dark matter halo and satellite population. The investigators will perform new suites of cosmological simulations constrained to match the Milky Way, with initial conditions appropriate for a variety of dark matter and early-universe scenarios, which will be used to calibrate the Galacticus galaxy formation model. The calibrated model, Galacticus-MW, will rapidly and accurately predict the Milky Way satellite population as a function of the beyond-CDM linear matter power spectrum. Comparing these predictions to the data will yield the first near-field measurement of small-scale matter clustering, along with constraints on dark matter properties (including its particle mass, interactions, and production mechanism) and on cosmic inflation. This work will enable cosmological inference using dwarf galaxy populations detected by Stage IV surveys over the next decade. 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.