The Observational Quest for the Least Massive Galaxies in the Universe
William Cerny
Yale University
Large-scale digital sky surveys have vastly improved our sensitivity to faint, low-mass, resolved stellar systems in the local universe, pushing us closer to discovering the very threshold of galaxy formation and enabling new tests of particle dark matter models. I will first describe recent efforts to discover ultra-faint dwarf galaxies and star clusters in the Galactic halo and beyond with the Dark Energy Camera, with a particular focus on systems discovered in recent years that push the luminosity and surface brightness frontier. I will then describe the discovery and spectroscopic characterization of the growing population of “ultra-faint star clusters” – the least luminous old stellar populations yet identified– and make the detailed case that some of these compact, extremely-low-mass systems may actually be the smallest galaxies. Lastly, I will conclude by highlighting promising individual candidates for the least massive galaxies in the universe (down to stellar masses < 200 Msun) and discuss the implications for the population of ultra-faint systems discoverable by the upcoming Vera C. Rubin Observatory and for galaxy formation physics more broadly.
Hosted by Prof. Kirby