The Dark Energy Survey: Redshifts, X-ray Temperatures and Luminosities for Galaxy CLusters within Science Verification Data

We present a joint analysis of the Dark Energy Survey (DES) Science Verification data and the {\it XMM} Cluster Survey (XCS). We identify $\sim 200$ galaxy clusters covering a wide range of redshifts ($0.03 \le z \le 1.25$) and temperatures ($1 \le T_{\rm X} \le 11$ keV). The median redshift of the sample is $z \sim 0.4$ and the median temperature is $T_{\rm X} = \sim 3$ keV. A majority are newly discovered clusters. We use a combination of archival and new spectroscopy to calibrate photometric redshifts to 1\% precision and sub-percent accuracy. We examine a number of possible systematic effects which could bias the photometric redshift determinations including deblending in cluster cores, magnitude definitions, and photometric accuracy. We highlight the quality of the Dark Energy Survey data and the promise of large-area joint optical/X-ray galaxy cluster samples.