Dark Energy Survey Year 1 Results: Cross-Correlation Redshifts in the
  DES -- Calibration of the Weak Lensing Source Redshift Distributions
  We present the calibration of the Dark Energy Survey Year 1 (DES Y1) weak
lensing source galaxy redshift distributions from clustering measurements. By
cross-correlating the positions of source galaxies with luminous red galaxies
selected by the redMaGiC algorithm we measure the redshift distributions of the
source galaxies as placed into different tomographic bins. These measurements
constrain any such shifts to an accuracy of $\sim0.02$ and can be computed even
when the clustering measurements do not span the full redshift range. The
highest-redshift source bin is not constrained by the clustering measurements
because of the minimal redshift overlap with the redMaGiC galaxies. We compare
our constraints with those obtained from $\texttt{COSMOS}$ 30-band photometry
and find that our two very different methods produce consistent constraints.
