Results from a High-Sensitivity Search for Cosmic Axions

We report the first results of a high-sensitivity $(\ensuremath{\sim}{10}^{\ensuremath{-}23}\mathrm{W})$ search for light halo axions through their conversion to microwave photons. At the 90% confidence level, we exclude a Kim-Shifman-Vainshtein-Zakharov axion of mass $2.9\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$ to $3.3\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}\mathrm{eV}$ as the dark matter in the halo of our galaxy.