Dark Energy Survey Year 1 Results: Galaxy Sample for BAO Measurement

TL;DR

This paper presents a carefully selected galaxy sample from the Dark Energy Survey Year 1 data, optimized for BAO measurements despite redshift uncertainties, and validates its properties and systematics.

Contribution

It defines a galaxy sample optimized for BAO analysis with detailed characterization, validation, and systematic mitigation strategies.

Findings

Sample contains 1.3 million galaxies at z > 0.6.

Photometric redshift uncertainties are 2.3% to 3.6%.

Clustering measurements are consistent with models.

Abstract

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.