FEEDBACK MODELS AND BURSTY STAR FORMATION HISTORIES IN DWARF GALAXIES

Abstract

To address tensions between DM-only simulations and observations on smaller scales, simulations implementing baryonic feedback have successfully produced galaxies with ``cored'' DM density profiles that are observed in nature and in conflict with the ``cuspy'' profiles predicted by $\Lambda$ for low-mass galaxies. The goal of this thesis is to address this cusp-core problem for $\Lambda$CDM simulations by introducing a robust comparison of the relationship between bursty star formation, or burstiness, and DM cores using two distinct SN feedback models with different sub-grid physics. This work analyzes two runs of the Storm simulation from the MARVEL suite of dwarf galaxies (one with blastwave feedback and one with superbubble feedback) by calculating various forms of burstiness for the Storm dwarf galaxies and comparing them to the DM density profile of the corresponding DM halo. This is achieved by comparing burstiness and DM core slopes, or the variation of the density profile for a chosen radial distance from the center of the galaxy, over the entire cosmic timescale and the time period of active star formation for each halo to determine that DM core formation and sustainment is correlated to higher values of burstiness. This work finds that there is a general trend between burstiness and the DM density profile, and that DM cores are efficiently sustained in the higher dwarf galaxy mass regime where star formation is burstier while the majority of ultra-faint and classical dwarf galaxies retain cuspy central DM density profiles regardless of feedback model. In addition, this work quantifies how strongly burstiness and DM core slopes depend on the stellar mass fraction, M$_*/$M$_{halo}$, and finds that core formation may be better predicted by M$_*/$M$_{halo}$ than burstiness as peak core formation occurs at different values of the stellar mass fraction for a given feedback model. Testing the robustness of the burstiness and core slope relation in this work improves our understanding of the cusp-core problem under the $\Lambda$CDM paradigm by constraining cored DM profiles to the higher dwarf galaxy mass regime and provides observational predictions on the SFHs and density profiles of classical dwarfs and UFDs that are expected to increase in discovery with upcoming surveys from the James Webb Space Telescope (JWST), Vera Rubin Observatory (VRO), and the Nancy Grace Roman Space Telescope (Roman).