KECK-I MOSFIRE SPECTROSCOPY OF THE z ∼ 12 CANDIDATE GALAXY UDFj-39546284**The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation.
Article in The Astrophysical Journal Letters (July 2013)