Three Ly Emitters at z 6: Early GMOS/Gemini Data from the GLARE Project

We report spectroscopic detection of three z~6 Lyman-alpha emitting galaxies,in the vicinity of the Hubble Ultra Deep Field, from the early data of theGemini Lyman-$\alpha$ at Reionisation Era (GLARE) project. Two objects,GLARE#3001 (z =5.79) and GLARE#3011 (z =5.94), are new detections and arefainter in $z'$ (z'_{AB} =26.37 and 27.15) than any Lyman break galaxypreviously detected in Lyman-alpha. A third object, GLARE#1042 (z =5.83) haspreviously been detected in line emission from the ground; we report here a newspectroscopic continuum detection. Gemini/GMOS-S spectra of these objects,obtained using nod & shuffle, are presented together with a discussion of theirphotometric properties. All three objects were selected for spectroscopy viathe i-drop Lyman Break technique, the two new detections from the GOODS v1.0imaging data. The red i'-z' colors and high equivalent widths of these objectssuggest a high-confidence z>5 Lyman-alpha identification of the emission lines.This brings the total number of known z>5 galaxies within 9 arcmin of theHubble Ultra Deep Field to four, of which three are at the same redshift (z=5.8within 2000 km/s suggesting the existence of a large-scale structure at thisredshift.Comment: 5 pages, 2 figures. Revised to match accepted versio