  We present a mass map reconstructed from weak gravitational lensing shear
measurements over 139 sq. deg from the Dark Energy Survey (DES) Science
Verification data. The mass map probes both luminous and dark matter, thus
providing a tool for studying cosmology. We find good agreement between the
mass map and the distribution of massive galaxy clusters identified using a
red-sequence cluster finder. Potential candidates for super-clusters and voids
are identified using these maps. We measure the cross-correlation between the
mass map and a magnitude-limited foreground galaxy sample and find a detection
at the 5-7 sigma level on a large range of scales. These measurements are
consistent with simulated galaxy catalogs based on LCDM N-body simulations,
suggesting low systematics uncertainties in the map. We summarize our key
findings in this letter; the detailed methodology and tests for systematics are
presented in a companion paper.
