We present some of the first high-resolution spectroscopic
metallicities of stars in the recently discovered ultra-faint dwarf
galaxies around the Milky Way. These galaxies have mean metallicities
as low as [Fe/H] = -2.6, more metal-poor than the least-enriched
globular clusters. We measure the abundances of Fe, Mg, Ca, Ti, Sc,
Sr, Ba, and C and show that the ultra-faint dwarfs have high
abundances of alpha elements and low abundances of neutron capture
species. At least some of the ultra-faint dwarfs contain large
abundance spreads, demonstrating that either these systems do not
consist of simple stellar populations or chemical mixing within them
was inefficient. We also find similarities between the observed
abundance patterns and those seen in halo stars. We discuss these
results in the context of the formation of the ultra-faint dwarfs and
the origin of metal-poor stars in the halo of the Milky Way.
To begin viewing slides, click on the first slide below. (Or, view as pdf.)