Dark Energy Survey Year 1 Results: Calibration of redMaGiC Redshift
  Distributions in DES and SDSS from Cross-Correlations
  We present calibrations of the redshift distributions of redMaGiC galaxies in
the Dark Energy Survey Year 1 (DES Y1) and Sloan Digital Sky Survey (SDSS) DR8
data. These results determine the priors of the redshift distribution of
redMaGiC galaxies, which were used for galaxy clustering measurements and as
lenses for galaxy-galaxy lensing measurements in DES Y1 cosmological analyses.
We empirically determine the bias in redMaGiC photometric redshift estimates
using angular cross-correlations with Baryon Oscillation Spectroscopic Survey
(BOSS) galaxies. For DES, we calibrate a single parameter redshift bias in
three photometric redshift bins: $z \in[0.15,0.3]$, [0.3,0.45], and [0.45,0.6].
Our best fit results in each bin give photometric redshift biases of $|\Delta
z|<0.01$. To further test the redMaGiC algorithm, we apply our calibration
procedure to SDSS redMaGiC galaxies, where the statistical precision of the
cross-correlation measurement is much higher due to a greater overlap with BOSS
galaxies. For SDSS, we also find best fit results of $|\Delta z|<0.01$. We
compare our results to other analyses of redMaGiC photometric redshifts.
