Dark Energy Survey Year 1 Results: Galaxy Sample for BAO Measurement
  We define and characterise a sample of 1.3 million galaxies extracted from
the first year of Dark Energy Survey data, optimised to measure Baryon Acoustic
Oscillations in the presence of significant redshift uncertainties. The sample
is dominated by luminous red galaxies located at redshifts $z \gtrsim 0.6$. We
define the exact selection using color and magnitude cuts that balance the need
of high number densities and small photometric redshift uncertainties, using
the corresponding forecasted BAO distance error as a figure-of-merit in the
process. The typical photo-$z$ uncertainty varies from $2.3\%$ to $3.6\%$ (in
units of 1+$z$) from $z=0.6$ to $1$, with number densities from $200$ to $130$
galaxies per deg$^2$ in tomographic bins of width $\Delta z = 0.1$. Next we
summarise the validation of the photometric redshift estimation. We
characterise and mitigate observational systematics including stellar
contamination, and show that the clustering on large scales is robust in front
of those contaminants. We show that the clustering signal in the
auto-correlations and cross-correlations is generally consistent with
theoretical models, which serves as an additional test of the redshift
distributions.
