SBS0335-052W: The lowest metallicity star-forming galaxy known

We present 4 m Kitt Peak telescope and 6.5 m MMT spectrophotometry of the extremely low metallicity galaxy SBS 0335-052W, the western companion of the blue compact dwarf galaxy SBS 0335-052E. These observations have been combined with published 10m Keck data to derive for the brightest region of SBS 0335 - 052Wan oxygen abundance 12 + log O/H 7.12 +/- 0: 03. This makes SBS 0335 - 052W the lowest metallicity star-forming galaxy known in the local universe. Using a Monte Carlo technique, we fit the spectral energy distribution of SBS 0335 - 052W to derive the age of the oldest stars contributing to its optical light. We find that star formation in SBS 0335 - 052W began less than 500 Myr ago, making it a likely nearby young dwarf galaxy.