CHAPTER 20: Stellar, Milky Way and Local Group Science

The Dark Energy Survey (DES) was established to study the properties of hundreds of millions of distant galaxies, in order to learn more about why the expansion of the universe is speeding up. However, it quickly became obvious that the survey could also be used to study objects in and around our home Galaxy, the Milky Way. The Dark Energy Camera (DECam) was the first super-sensitive, wide-field digital camera to operate in the southern hemisphere and this represented an amazing opportunity. Within the first season of observations, scientists using DES data discovered eight new satellite dwarf galaxies of the Milky Way, and by the end of the second year, we had found a total of seventeen dwarf galaxies. In this chapter, we explain how new data is enabling us to characterize the structure, mass assembly and star formation history of our Milky Way Galaxy, and to improve the census of low-mass and low-luminosity stars and sub-stellar objects. DES Milky Way working group attempts to address fundamental questions in Galactic archaeology and near-field cosmology such as what can we learn about the nature of dark matter from its distribution in and around the Milky Way? How was the Milky Way formed? and How do environmental effects influence the formation and evolution of galaxies?