Searching for the Faintest Galaxies with the Dark Energy Camera

Ultra-faint dwarf galaxies are among the oldest, faintest, and most dark-matter-dominated stellar systems known. As extreme systems, they are excellent laboratories for probing the fundamental nature of dark matter and the physics of galaxy formation. Over the last 10 years, the number of known ultra-faint dwarf galaxies has nearly quadrupled due to advances in large optical/near-infrared sky surveys. The Dark Energy Camera (DECam) on the 4-m Blanco Telescope at the Cerro Tololo Inter-American Observatory in Chile has been used to discover more ultra-faint dwarf galaxies than any other telescope+instrument system. I will present an overview of the technical and algorithmic advances that make DECam such a powerful ultra-faint dwarf galaxy discovery machine, with a specific focus on the DECam Local Volume Exploration survey (DELVE). The DELVE program combines new imaging with archival DECam data to cover >20,000 deg² of the high-Galactic-latitude sky and perform deeper imaging around the Magellanic Clouds and isolated Magellanic analogues in the Local Volume. I will discuss the properties of the known population of ultra-faint dwarf galaxies, and consider what current data may imply for forthcoming searches for ultra-faint dwarfs with the Vera C. Rubin Observatory’s Legacy Survey of Space and Time.