RUI: Unlocking the Origins of Ultra-Diffuse Galaxies

Ultra-diffuse galaxies (UDGs) are comparable in size to ordinary spirals but have dwarf galaxy-like luminosities. As a result, they possess extremely low surface brightness, and as a consequence, significant numbers have only fairly recently been cataloged. There is currently no coherent explanation for UDGs, and their surprising range of properties (e.g., some UDGs are dark matter dominated while others appear to lack dark matter altogether) suggest multiple formation pathways. The research team will tease apart potentially distinct paths of UDG origins through the integration of observations and theory for a large sample of UDGs. Undergraduate students represent an integral part of this research project and will have opportunities to make high impact discoveries. This project will also have synergies with the Cal-Bridge program. The research will combine photometric and spectroscopic data obtained with 8 and 10m-class telescopes and state-of-the-art simulations of galaxy and star cluster evolution in a cosmological context. The fundamental properties to be studied include UDG star formation histories, chemical abundance patterns, angular momentum, dynamical structure, dark matter content, globular cluster (GC) populations, and infall times. Key project goals include: (1) determining whether GC-rich and GC-poor UDGs belong to distinctly different families, (2) establishing the evolutionary connections between UDGs in different environments, (3) between UDGs and other dwarfs, (4) testing a new formation model for galaxies with no dark matter, and (5) identifying more examples of these galaxies. 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.